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	$100.25	11.328%	$111.6063	$111.61	$111.60	$111.60
Purchase #2	$13.54	10.359%	$14.9426	$14.94	$14.95	$14.90
Purchase #3	$207.77	8.468%	$225.364	$225.36	$225.35	$225.40
Purchase #4	$32.80	3.594%	$33.9788	$33.98	$34.00	$34.00
Purchase #5	$77.34	3.730%	$80.2248	$80.22	$80.20	$80.20
Purchase #6	$160.93	13.604%	$182.8229	$182.82	$182.80	$182.80
Purchase #7	$170.73	6.767%	$182.2833	$182.28	$182.30	$182.30
7 purchase totals =	$763.36		$831.2227	$831.21	$831.20	$831.20