Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$170.92	11.191%	$190.0477	$190.05	$190.05	$190.00
Purchase #2	$62.60	7.218%	$67.1185	$67.12	$67.10	$67.10
Purchase #3	$131.36	7.412%	$141.0964	$141.10	$141.10	$141.10
Purchase #4	$225.25	8.646%	$244.7251	$244.73	$244.75	$244.70
Purchase #5	$175.51	9.172%	$191.6078	$191.61	$191.60	$191.60
Purchase #6	$100.37	3.731%	$104.1148	$104.11	$104.10	$104.10
Purchase #7	$170.30	11.601%	$190.0565	$190.06	$190.05	$190.10
7 purchase totals =	$1,036.31		$1,128.7668	$1,128.78	$1,128.75	$1,128.70