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	$172.48	5.723%	$182.351	$182.35	$182.35	$182.40
Purchase #2	$199.27	9.203%	$217.6088	$217.61	$217.60	$217.60
Purchase #3	$38.76	12.253%	$43.5093	$43.51	$43.50	$43.50
Purchase #4	$110.80	13.360%	$125.6029	$125.60	$125.60	$125.60
Purchase #5	$116.44	5.820%	$123.2168	$123.22	$123.20	$123.20
Purchase #6	$75.34	4.706%	$78.8855	$78.89	$78.90	$78.90
Purchase #7	$149.74	6.687%	$159.7531	$159.75	$159.75	$159.80
7 purchase totals =	$862.83		$930.9274	$930.93	$930.90	$931.00