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	$37.59	11.396%	$41.8738	$41.87	$41.85	$41.90
Purchase #2	$74.72	4.488%	$78.0734	$78.07	$78.05	$78.10
Purchase #3	$231.50	5.658%	$244.5983	$244.60	$244.60	$244.60
Purchase #4	$186.79	13.476%	$211.9618	$211.96	$211.95	$212.00
Purchase #5	$63.58	11.871%	$71.1276	$71.13	$71.15	$71.10
Purchase #6	$214.85	8.707%	$233.557	$233.56	$233.55	$233.60
Purchase #7	$11.90	12.259%	$13.3588	$13.36	$13.35	$13.40
7 purchase totals =	$820.93		$894.5507	$894.55	$894.50	$894.70