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	$154.90	7.113%	$165.918	$165.92	$165.90	$165.90
Purchase #2	$242.67	3.395%	$250.9086	$250.91	$250.90	$250.90
Purchase #3	$197.53	4.640%	$206.6954	$206.70	$206.70	$206.70
Purchase #4	$55.77	10.434%	$61.589	$61.59	$61.60	$61.60
Purchase #5	$47.42	3.216%	$48.945	$48.95	$48.95	$48.90
Purchase #6	$47.92	8.148%	$51.8245	$51.82	$51.80	$51.80
Purchase #7	$61.61	7.528%	$66.248	$66.25	$66.25	$66.20
7 purchase totals =	$807.82		$852.1285	$852.14	$852.10	$852.00