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	$63.77	13.590%	$72.4363	$72.44	$72.45	$72.40
Purchase #2	$210.33	7.359%	$225.8082	$225.81	$225.80	$225.80
Purchase #3	$120.78	4.451%	$126.1559	$126.16	$126.15	$126.20
Purchase #4	$115.55	6.700%	$123.2919	$123.29	$123.30	$123.30
Purchase #5	$33.58	6.363%	$35.7167	$35.72	$35.70	$35.70
Purchase #6	$66.33	8.657%	$72.0722	$72.07	$72.05	$72.10
Purchase #7	$6.39	4.197%	$6.6582	$6.66	$6.65	$6.70
7 purchase totals =	$616.73		$662.1394	$662.15	$662.10	$662.20