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	$101.54	3.688%	$105.2848	$105.28	$105.30	$105.30
Purchase #2	$163.53	7.401%	$175.6329	$175.63	$175.65	$175.60
Purchase #3	$95.82	10.504%	$105.8849	$105.88	$105.90	$105.90
Purchase #4	$63.69	4.714%	$66.6923	$66.69	$66.70	$66.70
Purchase #5	$213.59	8.203%	$231.1108	$231.11	$231.10	$231.10
Purchase #6	$37.30	7.241%	$40.0009	$40.00	$40.00	$40.00
Purchase #7	$26.54	7.820%	$28.6154	$28.62	$28.60	$28.60
7 purchase totals =	$702.01		$753.2220	$753.21	$753.25	$753.20