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	$146.32	3.804%	$151.886	$151.89	$151.90	$151.90
Purchase #2	$146.27	12.840%	$165.0511	$165.05	$165.05	$165.10
Purchase #3	$235.68	11.741%	$263.3512	$263.35	$263.35	$263.40
Purchase #4	$19.34	3.456%	$20.0084	$20.01	$20.00	$20.00
Purchase #5	$208.95	7.161%	$223.9129	$223.91	$223.90	$223.90
Purchase #6	$153.92	5.244%	$161.9916	$161.99	$162.00	$162.00
Purchase #7	$93.76	7.155%	$100.4685	$100.47	$100.45	$100.50
7 purchase totals =	$1,004.24		$1,086.6697	$1,086.67	$1,086.65	$1,086.80