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	$198.53	13.550%	$225.4308	$225.43	$225.45	$225.40
Purchase #2	$20.40	7.462%	$21.9222	$21.92	$21.90	$21.90
Purchase #3	$234.84	11.786%	$262.5182	$262.52	$262.50	$262.50
Purchase #4	$227.52	11.719%	$254.1831	$254.18	$254.20	$254.20
Purchase #5	$57.86	11.153%	$64.3131	$64.31	$64.30	$64.30
Purchase #6	$243.77	10.705%	$269.8656	$269.87	$269.85	$269.90
Purchase #7	$101.40	9.575%	$111.1091	$111.11	$111.10	$111.10
7 purchase totals =	$1,084.32		$1,209.3421	$1,209.34	$1,209.30	$1,209.30