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	$140.91	10.178%	$155.2518	$155.25	$155.25	$155.30
Purchase #2	$159.52	8.363%	$172.8607	$172.86	$172.85	$172.90
Purchase #3	$59.97	12.136%	$67.248	$67.25	$67.25	$67.20
Purchase #4	$146.51	5.147%	$154.0509	$154.05	$154.05	$154.10
Purchase #5	$50.82	7.400%	$54.5807	$54.58	$54.60	$54.60
Purchase #6	$65.96	10.469%	$72.8654	$72.87	$72.85	$72.90
Purchase #7	$67.67	7.319%	$72.6228	$72.62	$72.60	$72.60
7 purchase totals =	$691.36		$749.4803	$749.48	$749.45	$749.60