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	$48.53	11.148%	$53.9401	$53.94	$53.95	$53.90
Purchase #2	$142.64	4.201%	$148.6323	$148.63	$148.65	$148.60
Purchase #3	$116.87	11.413%	$130.2084	$130.21	$130.20	$130.20
Purchase #4	$103.60	7.857%	$111.7399	$111.74	$111.75	$111.70
Purchase #5	$112.95	13.130%	$127.7803	$127.78	$127.80	$127.80
Purchase #6	$132.64	3.340%	$137.0702	$137.07	$137.05	$137.10
Purchase #7	$36.67	3.329%	$37.8907	$37.89	$37.90	$37.90
7 purchase totals =	$693.90		$747.2619	$747.26	$747.30	$747.20