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	$232.61	13.707%	$264.4939	$264.49	$264.50	$264.50
Purchase #2	$6.32	13.673%	$7.1841	$7.18	$7.20	$7.20
Purchase #3	$51.74	9.598%	$56.706	$56.71	$56.70	$56.70
Purchase #4	$97.27	12.775%	$109.6962	$109.70	$109.70	$109.70
Purchase #5	$189.82	3.502%	$196.4675	$196.47	$196.45	$196.50
Purchase #6	$105.68	5.836%	$111.8475	$111.85	$111.85	$111.80
Purchase #7	$143.57	11.105%	$159.5134	$159.51	$159.50	$159.50
7 purchase totals =	$827.01		$905.9086	$905.91	$905.90	$905.90