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	$246.37	3.776%	$255.6729	$255.67	$255.65	$255.70
Purchase #2	$99.80	9.350%	$109.1313	$109.13	$109.15	$109.10
Purchase #3	$165.43	3.434%	$171.1109	$171.11	$171.10	$171.10
Purchase #4	$139.88	13.808%	$159.1946	$159.19	$159.20	$159.20
Purchase #5	$151.58	13.462%	$171.9857	$171.99	$172.00	$172.00
Purchase #6	$106.63	9.635%	$116.9038	$116.90	$116.90	$116.90
Purchase #7	$111.82	10.423%	$123.475	$123.48	$123.50	$123.50
7 purchase totals =	$1,021.51		$1,107.4742	$1,107.47	$1,107.50	$1,107.50