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	$175.36	13.635%	$199.2703	$199.27	$199.25	$199.30
Purchase #2	$75.86	13.137%	$85.8257	$85.83	$85.85	$85.80
Purchase #3	$190.70	3.319%	$197.0293	$197.03	$197.05	$197.00
Purchase #4	$158.26	4.381%	$165.1934	$165.19	$165.20	$165.20
Purchase #5	$166.70	11.478%	$185.8338	$185.83	$185.85	$185.80
Purchase #6	$44.54	11.121%	$49.4933	$49.49	$49.50	$49.50
Purchase #7	$122.52	11.203%	$136.2459	$136.25	$136.25	$136.20
7 purchase totals =	$933.94		$1,018.8917	$1,018.89	$1,018.95	$1,018.80