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	$42.65	6.111%	$45.2563	$45.26	$45.25	$45.30
Purchase #2	$18.70	13.656%	$21.2537	$21.25	$21.25	$21.30
Purchase #3	$89.47	3.371%	$92.486	$92.49	$92.50	$92.50
Purchase #4	$181.65	6.672%	$193.7697	$193.77	$193.75	$193.80
Purchase #5	$71.38	9.603%	$78.2346	$78.23	$78.25	$78.20
Purchase #6	$106.72	9.146%	$116.4806	$116.48	$116.50	$116.50
Purchase #7	$246.41	3.813%	$255.8056	$255.81	$255.80	$255.80
7 purchase totals =	$756.98		$803.2865	$803.29	$803.30	$803.40