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	$80.59	7.266%	$86.4457	$86.45	$86.45	$86.40
Purchase #2	$218.75	6.820%	$233.6688	$233.67	$233.65	$233.70
Purchase #3	$29.51	11.646%	$32.9467	$32.95	$32.95	$32.90
Purchase #4	$20.41	10.289%	$22.51	$22.51	$22.50	$22.50
Purchase #5	$203.87	9.496%	$223.2295	$223.23	$223.25	$223.20
Purchase #6	$234.89	10.373%	$259.2551	$259.26	$259.25	$259.30
Purchase #7	$33.37	10.317%	$36.8128	$36.81	$36.80	$36.80
7 purchase totals =	$821.39		$894.8686	$894.88	$894.85	$894.80