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	$175.53	12.504%	$197.4783	$197.48	$197.50	$197.50
Purchase #2	$209.35	11.367%	$233.1468	$233.15	$233.15	$233.10
Purchase #3	$48.43	8.621%	$52.6052	$52.61	$52.60	$52.60
Purchase #4	$75.65	3.496%	$78.2947	$78.29	$78.30	$78.30
Purchase #5	$37.87	13.267%	$42.8942	$42.89	$42.90	$42.90
Purchase #6	$222.38	12.590%	$250.3776	$250.38	$250.40	$250.40
Purchase #7	$74.61	11.387%	$83.1058	$83.11	$83.10	$83.10
7 purchase totals =	$843.82		$937.9026	$937.91	$937.95	$937.90