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	$231.81	8.121%	$250.6353	$250.64	$250.65	$250.60
Purchase #2	$136.71	8.391%	$148.1813	$148.18	$148.20	$148.20
Purchase #3	$233.32	3.350%	$241.1362	$241.14	$241.15	$241.10
Purchase #4	$10.82	6.576%	$11.5315	$11.53	$11.55	$11.50
Purchase #5	$137.85	10.682%	$152.5751	$152.58	$152.60	$152.60
Purchase #6	$171.70	10.590%	$189.883	$189.88	$189.90	$189.90
Purchase #7	$18.82	5.699%	$19.8926	$19.89	$19.90	$19.90
7 purchase totals =	$941.03		$1,013.8350	$1,013.84	$1,013.95	$1,013.80