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	$221.43	6.252%	$235.2738	$235.27	$235.25	$235.30
Purchase #2	$219.30	10.461%	$242.241	$242.24	$242.25	$242.20
Purchase #3	$197.94	3.314%	$204.4997	$204.50	$204.50	$204.50
Purchase #4	$123.98	13.400%	$140.5933	$140.59	$140.60	$140.60
Purchase #5	$109.83	13.644%	$124.8152	$124.82	$124.80	$124.80
Purchase #6	$66.75	8.326%	$72.3076	$72.31	$72.30	$72.30
Purchase #7	$216.31	4.211%	$225.4188	$225.42	$225.40	$225.40
7 purchase totals =	$1,155.54		$1,245.1494	$1,245.15	$1,245.10	$1,245.10