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	$30.46	7.863%	$32.8551	$32.86	$32.85	$32.90
Purchase #2	$124.43	11.633%	$138.9049	$138.90	$138.90	$138.90
Purchase #3	$84.63	3.161%	$87.3052	$87.31	$87.30	$87.30
Purchase #4	$209.99	6.466%	$223.568	$223.57	$223.55	$223.60
Purchase #5	$93.26	13.103%	$105.4799	$105.48	$105.50	$105.50
Purchase #6	$193.38	6.298%	$205.5591	$205.56	$205.55	$205.60
Purchase #7	$55.47	6.572%	$59.1155	$59.12	$59.10	$59.10
7 purchase totals =	$791.62		$852.7877	$852.80	$852.75	$852.90