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	$82.95	10.805%	$91.9127	$91.91	$91.90	$91.90
Purchase #2	$71.85	9.273%	$78.5127	$78.51	$78.50	$78.50
Purchase #3	$66.55	6.118%	$70.6215	$70.62	$70.60	$70.60
Purchase #4	$125.52	9.324%	$137.2235	$137.22	$137.20	$137.20
Purchase #5	$214.60	4.460%	$224.1712	$224.17	$224.15	$224.20
Purchase #6	$134.53	8.823%	$146.3996	$146.40	$146.40	$146.40
Purchase #7	$150.46	6.453%	$160.1692	$160.17	$160.15	$160.20
7 purchase totals =	$846.46		$909.0104	$909.00	$908.90	$909.00