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	$164.83	4.628%	$172.4583	$172.46	$172.45	$172.50
Purchase #2	$56.46	5.461%	$59.5433	$59.54	$59.55	$59.50
Purchase #3	$118.47	3.461%	$122.5702	$122.57	$122.55	$122.60
Purchase #4	$25.63	3.774%	$26.5973	$26.60	$26.60	$26.60
Purchase #5	$38.46	12.816%	$43.389	$43.39	$43.40	$43.40
Purchase #6	$247.57	10.288%	$273.04	$273.04	$273.05	$273.00
Purchase #7	$6.88	3.308%	$7.1076	$7.11	$7.10	$7.10
7 purchase totals =	$658.30		$704.7057	$704.71	$704.70	$704.70