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	$93.63	12.638%	$105.463	$105.46	$105.45	$105.50
Purchase #2	$140.43	9.713%	$154.07	$154.07	$154.05	$154.10
Purchase #3	$140.78	8.569%	$152.8434	$152.84	$152.85	$152.80
Purchase #4	$155.80	9.437%	$170.5028	$170.50	$170.50	$170.50
Purchase #5	$127.58	10.104%	$140.4707	$140.47	$140.45	$140.50
Purchase #6	$158.68	7.761%	$170.9952	$171.00	$171.00	$171.00
Purchase #7	$114.66	7.590%	$123.3627	$123.36	$123.35	$123.40
7 purchase totals =	$931.56		$1,017.7078	$1,017.70	$1,017.65	$1,017.80