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	$144.76	5.864%	$153.2487	$153.25	$153.25	$153.20
Purchase #2	$217.45	13.610%	$247.0449	$247.04	$247.05	$247.00
Purchase #3	$155.82	12.523%	$175.3333	$175.33	$175.35	$175.30
Purchase #4	$57.78	11.353%	$64.3398	$64.34	$64.35	$64.30
Purchase #5	$40.39	5.322%	$42.5396	$42.54	$42.55	$42.50
Purchase #6	$43.78	5.709%	$46.2794	$46.28	$46.30	$46.30
Purchase #7	$76.54	13.676%	$87.0076	$87.01	$87.00	$87.00
7 purchase totals =	$736.52		$815.7933	$815.79	$815.85	$815.60