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	$173.59	10.120%	$191.1573	$191.16	$191.15	$191.20
Purchase #2	$34.83	6.345%	$37.04	$37.04	$37.05	$37.00
Purchase #3	$28.70	9.394%	$31.3961	$31.40	$31.40	$31.40
Purchase #4	$64.27	9.114%	$70.1276	$70.13	$70.15	$70.10
Purchase #5	$73.92	13.104%	$83.6065	$83.61	$83.60	$83.60
Purchase #6	$99.34	5.301%	$104.606	$104.61	$104.60	$104.60
Purchase #7	$12.71	8.197%	$13.7518	$13.75	$13.75	$13.80
7 purchase totals =	$487.36		$531.6853	$531.70	$531.70	$531.70