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	$54.58	9.237%	$59.6216	$59.62	$59.60	$59.60
Purchase #2	$52.90	3.846%	$54.9345	$54.93	$54.95	$54.90
Purchase #3	$243.47	13.453%	$276.224	$276.22	$276.20	$276.20
Purchase #4	$28.45	11.298%	$31.6643	$31.66	$31.65	$31.70
Purchase #5	$43.49	5.230%	$45.7645	$45.76	$45.75	$45.80
Purchase #6	$100.35	10.550%	$110.9369	$110.94	$110.95	$110.90
Purchase #7	$34.92	4.778%	$36.5885	$36.59	$36.60	$36.60
7 purchase totals =	$558.16		$615.7343	$615.72	$615.70	$615.70