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	$12.51	3.500%	$12.9479	$12.95	$12.95	$12.90
Purchase #2	$70.63	4.321%	$73.6819	$73.68	$73.70	$73.70
Purchase #3	$172.89	10.334%	$190.7565	$190.76	$190.75	$190.80
Purchase #4	$228.27	4.429%	$238.3801	$238.38	$238.40	$238.40
Purchase #5	$11.89	13.276%	$13.4685	$13.47	$13.45	$13.50
Purchase #6	$113.84	9.800%	$124.9963	$125.00	$125.00	$125.00
Purchase #7	$93.74	7.631%	$100.8933	$100.89	$100.90	$100.90
7 purchase totals =	$703.77		$755.1245	$755.13	$755.15	$755.20