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	$176.61	7.495%	$189.8469	$189.85	$189.85	$189.80
Purchase #2	$60.71	3.413%	$62.782	$62.78	$62.80	$62.80
Purchase #3	$190.61	7.560%	$205.0201	$205.02	$205.00	$205.00
Purchase #4	$158.86	4.428%	$165.8943	$165.89	$165.90	$165.90
Purchase #5	$143.67	11.368%	$160.0024	$160.00	$160.00	$160.00
Purchase #6	$137.53	13.658%	$156.3138	$156.31	$156.30	$156.30
Purchase #7	$36.94	11.733%	$41.2742	$41.27	$41.25	$41.30
7 purchase totals =	$904.93		$981.1337	$981.12	$981.10	$981.10