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	$128.35	9.620%	$140.6973	$140.70	$140.70	$140.70
Purchase #2	$68.40	6.419%	$72.7906	$72.79	$72.80	$72.80
Purchase #3	$90.44	5.733%	$95.6249	$95.62	$95.60	$95.60
Purchase #4	$36.57	3.446%	$37.8302	$37.83	$37.85	$37.80
Purchase #5	$36.46	7.650%	$39.2492	$39.25	$39.25	$39.20
Purchase #6	$233.61	10.603%	$258.3797	$258.38	$258.40	$258.40
Purchase #7	$130.44	11.747%	$145.7628	$145.76	$145.75	$145.80
7 purchase totals =	$724.27		$790.3347	$790.33	$790.35	$790.30