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	$101.80	12.133%	$114.1514	$114.15	$114.15	$114.20
Purchase #2	$108.80	13.606%	$123.6033	$123.60	$123.60	$123.60
Purchase #3	$37.69	6.664%	$40.2017	$40.20	$40.20	$40.20
Purchase #4	$85.83	3.627%	$88.9431	$88.94	$88.95	$88.90
Purchase #5	$30.45	10.317%	$33.5915	$33.59	$33.60	$33.60
Purchase #6	$60.27	10.512%	$66.6056	$66.61	$66.60	$66.60
Purchase #7	$8.51	6.170%	$9.0351	$9.04	$9.05	$9.00
7 purchase totals =	$433.35		$476.1317	$476.13	$476.15	$476.10