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	$57.62	7.491%	$61.9363	$61.94	$61.95	$61.90
Purchase #2	$150.56	13.508%	$170.8976	$170.90	$170.90	$170.90
Purchase #3	$230.53	10.367%	$254.429	$254.43	$254.45	$254.40
Purchase #4	$37.41	9.173%	$40.8416	$40.84	$40.85	$40.80
Purchase #5	$12.93	4.335%	$13.4905	$13.49	$13.50	$13.50
Purchase #6	$52.90	12.136%	$59.3199	$59.32	$59.30	$59.30
Purchase #7	$204.78	3.748%	$212.4552	$212.46	$212.45	$212.50
7 purchase totals =	$746.73		$813.3701	$813.38	$813.40	$813.30