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	$223.89	13.798%	$254.7823	$254.78	$254.80	$254.80
Purchase #2	$73.34	4.545%	$76.6733	$76.67	$76.65	$76.70
Purchase #3	$238.75	10.477%	$263.7638	$263.76	$263.75	$263.80
Purchase #4	$32.76	9.614%	$35.9095	$35.91	$35.90	$35.90
Purchase #5	$165.73	4.148%	$172.6045	$172.60	$172.60	$172.60
Purchase #6	$168.58	4.324%	$175.8694	$175.87	$175.85	$175.90
Purchase #7	$168.89	4.434%	$176.3786	$176.38	$176.40	$176.40
7 purchase totals =	$1,071.94		$1,155.9814	$1,155.97	$1,155.95	$1,156.10