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	$43.90	11.282%	$48.8528	$48.85	$48.85	$48.90
Purchase #2	$82.40	13.448%	$93.4812	$93.48	$93.50	$93.50
Purchase #3	$191.77	8.749%	$208.548	$208.55	$208.55	$208.50
Purchase #4	$146.86	4.257%	$153.1118	$153.11	$153.10	$153.10
Purchase #5	$29.75	9.257%	$32.504	$32.50	$32.50	$32.50
Purchase #6	$170.33	3.436%	$176.1825	$176.18	$176.20	$176.20
Purchase #7	$40.68	12.117%	$45.6092	$45.61	$45.60	$45.60
7 purchase totals =	$705.69		$758.2895	$758.28	$758.30	$758.30