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	$195.35	11.146%	$217.1237	$217.12	$217.10	$217.10
Purchase #2	$150.36	6.172%	$159.6402	$159.64	$159.65	$159.60
Purchase #3	$127.82	7.560%	$137.4832	$137.48	$137.50	$137.50
Purchase #4	$78.67	9.806%	$86.3844	$86.38	$86.40	$86.40
Purchase #5	$117.81	10.111%	$129.7218	$129.72	$129.70	$129.70
Purchase #6	$81.63	9.675%	$89.5277	$89.53	$89.55	$89.50
Purchase #7	$52.70	6.702%	$56.232	$56.23	$56.25	$56.20
7 purchase totals =	$804.34		$876.1130	$876.10	$876.15	$876.00