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	$198.59	7.657%	$213.796	$213.80	$213.80	$213.80
Purchase #2	$231.39	7.536%	$248.8276	$248.83	$248.85	$248.80
Purchase #3	$114.82	10.762%	$127.1769	$127.18	$127.20	$127.20
Purchase #4	$227.64	12.636%	$256.4046	$256.40	$256.40	$256.40
Purchase #5	$34.70	11.766%	$38.7828	$38.78	$38.80	$38.80
Purchase #6	$62.58	6.375%	$66.5695	$66.57	$66.55	$66.60
Purchase #7	$31.25	7.382%	$33.5569	$33.56	$33.55	$33.60
7 purchase totals =	$900.97		$985.1143	$985.12	$985.15	$985.20