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	$82.53	10.572%	$91.2551	$91.26	$91.25	$91.30
Purchase #2	$113.50	13.203%	$128.4854	$128.49	$128.50	$128.50
Purchase #3	$66.87	8.273%	$72.4022	$72.40	$72.40	$72.40
Purchase #4	$39.67	3.761%	$41.162	$41.16	$41.15	$41.20
Purchase #5	$52.59	7.394%	$56.4785	$56.48	$56.50	$56.50
Purchase #6	$42.85	5.652%	$45.2719	$45.27	$45.25	$45.30
Purchase #7	$155.77	10.598%	$172.2785	$172.28	$172.30	$172.30
7 purchase totals =	$553.78		$607.3336	$607.34	$607.35	$607.50