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	$151.61	12.149%	$170.0291	$170.03	$170.05	$170.00
Purchase #2	$115.89	4.523%	$121.1317	$121.13	$121.15	$121.10
Purchase #3	$225.63	8.307%	$244.3731	$244.37	$244.35	$244.40
Purchase #4	$123.27	4.186%	$128.4301	$128.43	$128.45	$128.40
Purchase #5	$137.43	4.573%	$143.7147	$143.71	$143.70	$143.70
Purchase #6	$80.33	10.794%	$89.0008	$89.00	$89.00	$89.00
Purchase #7	$131.78	4.132%	$137.2251	$137.23	$137.25	$137.20
7 purchase totals =	$965.94		$1,033.9046	$1,033.90	$1,033.95	$1,033.80