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	$216.72	5.839%	$229.3743	$229.37	$229.35	$229.40
Purchase #2	$226.82	12.576%	$255.3449	$255.34	$255.35	$255.30
Purchase #3	$140.25	4.760%	$146.9259	$146.93	$146.95	$146.90
Purchase #4	$108.66	5.843%	$115.009	$115.01	$115.00	$115.00
Purchase #5	$50.25	10.790%	$55.672	$55.67	$55.65	$55.70
Purchase #6	$210.87	9.463%	$230.8246	$230.82	$230.80	$230.80
Purchase #7	$11.74	9.816%	$12.8924	$12.89	$12.90	$12.90
7 purchase totals =	$965.31		$1,046.0431	$1,046.03	$1,046.00	$1,046.00