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	$250.60	9.375%	$274.0938	$274.09	$274.10	$274.10
Purchase #2	$75.87	8.515%	$82.3303	$82.33	$82.35	$82.30
Purchase #3	$11.45	13.753%	$13.0247	$13.02	$13.00	$13.00
Purchase #4	$7.40	6.874%	$7.9087	$7.91	$7.90	$7.90
Purchase #5	$90.42	4.610%	$94.5884	$94.59	$94.60	$94.60
Purchase #6	$157.47	9.723%	$172.7808	$172.78	$172.80	$172.80
Purchase #7	$233.43	5.749%	$246.8499	$246.85	$246.85	$246.80
7 purchase totals =	$826.64		$891.5766	$891.57	$891.60	$891.50