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	$211.97	12.145%	$237.7138	$237.71	$237.70	$237.70
Purchase #2	$90.91	9.871%	$99.8837	$99.88	$99.90	$99.90
Purchase #3	$37.52	7.122%	$40.1922	$40.19	$40.20	$40.20
Purchase #4	$175.54	11.389%	$195.5323	$195.53	$195.55	$195.50
Purchase #5	$84.38	3.243%	$87.1164	$87.12	$87.10	$87.10
Purchase #6	$198.96	10.327%	$219.5066	$219.51	$219.50	$219.50
Purchase #7	$99.29	9.845%	$109.0651	$109.07	$109.05	$109.10
7 purchase totals =	$898.57		$989.0101	$989.01	$989.00	$989.00