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	$33.75	10.838%	$37.4078	$37.41	$37.40	$37.40
Purchase #2	$57.50	10.635%	$63.6151	$63.62	$63.60	$63.60
Purchase #3	$88.37	12.207%	$99.1573	$99.16	$99.15	$99.20
Purchase #4	$78.29	12.492%	$88.07	$88.07	$88.05	$88.10
Purchase #5	$59.35	8.190%	$64.2108	$64.21	$64.20	$64.20
Purchase #6	$185.51	12.347%	$208.4149	$208.41	$208.40	$208.40
Purchase #7	$124.36	12.154%	$139.4747	$139.47	$139.45	$139.50
7 purchase totals =	$627.13		$700.3506	$700.35	$700.25	$700.40