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	$209.63	10.358%	$231.3435	$231.34	$231.35	$231.30
Purchase #2	$57.82	11.484%	$64.46	$64.46	$64.45	$64.50
Purchase #3	$53.96	8.569%	$58.5838	$58.58	$58.60	$58.60
Purchase #4	$91.32	8.714%	$99.2776	$99.28	$99.30	$99.30
Purchase #5	$62.56	13.431%	$70.9624	$70.96	$70.95	$71.00
Purchase #6	$175.96	5.606%	$185.8243	$185.82	$185.80	$185.80
Purchase #7	$73.41	13.233%	$83.1243	$83.12	$83.10	$83.10
7 purchase totals =	$724.66		$793.5759	$793.56	$793.55	$793.60