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	$24.94	4.781%	$26.1324	$26.13	$26.15	$26.10
Purchase #2	$111.83	9.134%	$122.0446	$122.04	$122.05	$122.00
Purchase #3	$98.80	10.847%	$109.5168	$109.52	$109.50	$109.50
Purchase #4	$126.75	13.850%	$144.3049	$144.30	$144.30	$144.30
Purchase #5	$37.36	9.143%	$40.7758	$40.78	$40.80	$40.80
Purchase #6	$88.34	13.597%	$100.3516	$100.35	$100.35	$100.40
Purchase #7	$125.46	5.340%	$132.1596	$132.16	$132.15	$132.20
7 purchase totals =	$613.48		$675.2857	$675.28	$675.30	$675.30