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	$33.75	13.244%	$38.2199	$38.22	$38.20	$38.20
Purchase #2	$145.53	8.394%	$157.7458	$157.75	$157.75	$157.70
Purchase #3	$37.47	12.451%	$42.1354	$42.14	$42.15	$42.10
Purchase #4	$51.96	10.122%	$57.2194	$57.22	$57.20	$57.20
Purchase #5	$50.58	7.394%	$54.3199	$54.32	$54.30	$54.30
Purchase #6	$124.45	11.797%	$139.1314	$139.13	$139.15	$139.10
Purchase #7	$212.77	6.112%	$225.7745	$225.77	$225.75	$225.80
7 purchase totals =	$656.51		$714.5463	$714.55	$714.50	$714.40