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	$231.65	13.821%	$263.6663	$263.67	$263.65	$263.70
Purchase #2	$35.88	5.377%	$37.8093	$37.81	$37.80	$37.80
Purchase #3	$117.81	11.482%	$131.3369	$131.34	$131.35	$131.30
Purchase #4	$88.63	8.159%	$95.8613	$95.86	$95.85	$95.90
Purchase #5	$124.80	13.817%	$142.0436	$142.04	$142.05	$142.00
Purchase #6	$189.77	10.333%	$209.3789	$209.38	$209.40	$209.40
Purchase #7	$113.85	10.776%	$126.1185	$126.12	$126.10	$126.10
7 purchase totals =	$902.39		$1,006.2148	$1,006.22	$1,006.20	$1,006.20