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	$30.65	4.474%	$32.0213	$32.02	$32.00	$32.00
Purchase #2	$248.47	13.282%	$281.4718	$281.47	$281.45	$281.50
Purchase #3	$211.66	4.493%	$221.1699	$221.17	$221.15	$221.20
Purchase #4	$49.99	7.453%	$53.7158	$53.72	$53.70	$53.70
Purchase #5	$173.31	13.642%	$196.953	$196.95	$196.95	$197.00
Purchase #6	$157.66	4.117%	$164.1509	$164.15	$164.15	$164.20
Purchase #7	$85.80	8.870%	$93.4105	$93.41	$93.40	$93.40
7 purchase totals =	$957.54		$1,042.8932	$1,042.89	$1,042.80	$1,043.00