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	$145.49	3.624%	$150.7626	$150.76	$150.75	$150.80
Purchase #2	$166.57	13.460%	$188.9903	$188.99	$189.00	$189.00
Purchase #3	$100.88	8.137%	$109.0886	$109.09	$109.10	$109.10
Purchase #4	$88.48	12.504%	$99.5435	$99.54	$99.55	$99.50
Purchase #5	$197.43	12.834%	$222.7682	$222.77	$222.75	$222.80
Purchase #6	$5.94	6.201%	$6.3083	$6.31	$6.30	$6.30
Purchase #7	$216.25	6.584%	$230.4879	$230.49	$230.50	$230.50
7 purchase totals =	$921.04		$1,007.9494	$1,007.95	$1,007.95	$1,008.00