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	$128.38	10.408%	$141.7418	$141.74	$141.75	$141.70
Purchase #2	$133.72	4.447%	$139.6665	$139.67	$139.65	$139.70
Purchase #3	$151.62	10.341%	$167.299	$167.30	$167.30	$167.30
Purchase #4	$50.46	3.367%	$52.159	$52.16	$52.15	$52.20
Purchase #5	$48.61	9.734%	$53.3417	$53.34	$53.35	$53.30
Purchase #6	$100.57	4.690%	$105.2867	$105.29	$105.30	$105.30
Purchase #7	$34.61	7.488%	$37.2016	$37.20	$37.20	$37.20
7 purchase totals =	$647.97		$696.6963	$696.70	$696.70	$696.70