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	$64.70	4.131%	$67.3728	$67.37	$67.35	$67.40
Purchase #2	$185.92	3.688%	$192.7767	$192.78	$192.80	$192.80
Purchase #3	$92.55	13.577%	$105.1155	$105.12	$105.10	$105.10
Purchase #4	$176.55	7.697%	$190.1391	$190.14	$190.15	$190.10
Purchase #5	$200.58	11.313%	$223.2716	$223.27	$223.25	$223.30
Purchase #6	$172.61	5.236%	$181.6479	$181.65	$181.65	$181.60
Purchase #7	$34.48	8.657%	$37.4649	$37.46	$37.45	$37.50
7 purchase totals =	$927.39		$997.7885	$997.79	$997.75	$997.80