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	$33.37	7.135%	$35.7509	$35.75	$35.75	$35.80
Purchase #2	$120.83	4.203%	$125.9085	$125.91	$125.90	$125.90
Purchase #3	$243.41	5.215%	$256.1038	$256.10	$256.10	$256.10
Purchase #4	$127.38	12.634%	$143.4732	$143.47	$143.45	$143.50
Purchase #5	$100.39	10.610%	$111.0414	$111.04	$111.05	$111.00
Purchase #6	$199.53	4.132%	$207.7746	$207.77	$207.75	$207.80
Purchase #7	$215.45	10.626%	$238.3437	$238.34	$238.35	$238.30
7 purchase totals =	$1,040.36		$1,118.3961	$1,118.38	$1,118.35	$1,118.40