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	$250.59	7.496%	$269.3742	$269.37	$269.35	$269.40
Purchase #2	$30.77	13.453%	$34.9095	$34.91	$34.90	$34.90
Purchase #3	$36.63	12.351%	$41.1542	$41.15	$41.15	$41.20
Purchase #4	$59.51	13.497%	$67.5421	$67.54	$67.55	$67.50
Purchase #5	$229.57	11.309%	$255.5321	$255.53	$255.55	$255.50
Purchase #6	$218.37	8.135%	$236.1344	$236.13	$236.15	$236.10
Purchase #7	$36.38	8.240%	$39.3777	$39.38	$39.40	$39.40
7 purchase totals =	$861.82		$944.0242	$944.01	$944.05	$944.00