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	$211.85	6.661%	$225.9613	$225.96	$225.95	$226.00
Purchase #2	$142.86	4.603%	$149.4358	$149.44	$149.45	$149.40
Purchase #3	$170.81	12.270%	$191.7684	$191.77	$191.75	$191.80
Purchase #4	$25.37	12.688%	$28.5889	$28.59	$28.60	$28.60
Purchase #5	$148.82	11.175%	$165.4506	$165.45	$165.45	$165.50
Purchase #6	$89.91	11.377%	$100.1391	$100.14	$100.15	$100.10
Purchase #7	$221.65	10.157%	$244.163	$244.16	$244.15	$244.20
7 purchase totals =	$1,011.27		$1,105.5071	$1,105.51	$1,105.50	$1,105.60