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	$170.84	12.734%	$192.5948	$192.59	$192.60	$192.60
Purchase #2	$85.96	4.234%	$89.5995	$89.60	$89.60	$89.60
Purchase #3	$10.89	4.787%	$11.4113	$11.41	$11.40	$11.40
Purchase #4	$120.48	4.242%	$125.5908	$125.59	$125.60	$125.60
Purchase #5	$215.82	12.733%	$243.3004	$243.30	$243.30	$243.30
Purchase #6	$50.35	4.354%	$52.5422	$52.54	$52.55	$52.50
Purchase #7	$62.36	4.854%	$65.387	$65.39	$65.40	$65.40
7 purchase totals =	$716.70		$780.4260	$780.42	$780.45	$780.40