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	$45.77	10.221%	$50.4482	$50.45	$50.45	$50.40
Purchase #2	$40.31	13.240%	$45.647	$45.65	$45.65	$45.60
Purchase #3	$143.83	3.443%	$148.7821	$148.78	$148.80	$148.80
Purchase #4	$54.78	12.755%	$61.7672	$61.77	$61.75	$61.80
Purchase #5	$121.83	12.576%	$137.1513	$137.15	$137.15	$137.20
Purchase #6	$96.37	10.776%	$106.7548	$106.75	$106.75	$106.80
Purchase #7	$168.41	8.630%	$182.9438	$182.94	$182.95	$182.90
7 purchase totals =	$671.30		$733.4944	$733.49	$733.50	$733.50