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	$192.83	12.800%	$217.5122	$217.51	$217.50	$217.50
Purchase #2	$21.74	3.683%	$22.5407	$22.54	$22.55	$22.50
Purchase #3	$208.82	3.865%	$216.8909	$216.89	$216.90	$216.90
Purchase #4	$52.28	12.650%	$58.8934	$58.89	$58.90	$58.90
Purchase #5	$74.43	10.382%	$82.1573	$82.16	$82.15	$82.20
Purchase #6	$139.35	5.245%	$146.6589	$146.66	$146.65	$146.70
Purchase #7	$165.71	9.558%	$181.5486	$181.55	$181.55	$181.50
7 purchase totals =	$855.16		$926.2020	$926.20	$926.20	$926.20