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	$216.95	3.709%	$224.9967	$225.00	$225.00	$225.00
Purchase #2	$105.89	7.858%	$114.2108	$114.21	$114.20	$114.20
Purchase #3	$14.50	4.441%	$15.1439	$15.14	$15.15	$15.10
Purchase #4	$67.66	7.198%	$72.5302	$72.53	$72.55	$72.50
Purchase #5	$56.96	8.362%	$61.723	$61.72	$61.70	$61.70
Purchase #6	$16.47	3.671%	$17.0746	$17.07	$17.05	$17.10
Purchase #7	$139.80	6.505%	$148.894	$148.89	$148.90	$148.90
7 purchase totals =	$618.23		$654.5732	$654.56	$654.55	$654.50