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	$69.88	5.570%	$73.7723	$73.77	$73.75	$73.80
Purchase #2	$204.61	5.631%	$216.1316	$216.13	$216.15	$216.10
Purchase #3	$144.55	9.575%	$158.3907	$158.39	$158.40	$158.40
Purchase #4	$37.61	11.173%	$41.8122	$41.81	$41.80	$41.80
Purchase #5	$230.72	7.125%	$247.1588	$247.16	$247.15	$247.20
Purchase #6	$82.94	11.496%	$92.4748	$92.47	$92.45	$92.50
Purchase #7	$207.44	11.650%	$231.6068	$231.61	$231.60	$231.60
7 purchase totals =	$977.75		$1,061.3472	$1,061.34	$1,061.30	$1,061.40