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	$137.37	11.194%	$152.7472	$152.75	$152.75	$152.70
Purchase #2	$145.36	9.659%	$159.4003	$159.40	$159.40	$159.40
Purchase #3	$126.84	10.804%	$140.5438	$140.54	$140.55	$140.50
Purchase #4	$11.45	12.216%	$12.8487	$12.85	$12.85	$12.80
Purchase #5	$51.72	13.549%	$58.7275	$58.73	$58.75	$58.70
Purchase #6	$92.34	8.479%	$100.1695	$100.17	$100.15	$100.20
Purchase #7	$98.34	13.260%	$111.3799	$111.38	$111.40	$111.40
7 purchase totals =	$663.42		$735.8169	$735.82	$735.85	$735.70