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	$243.34	9.510%	$266.4816	$266.48	$266.50	$266.50
Purchase #2	$103.51	13.311%	$117.2882	$117.29	$117.30	$117.30
Purchase #3	$236.95	13.584%	$269.1373	$269.14	$269.15	$269.10
Purchase #4	$123.74	12.438%	$139.1308	$139.13	$139.15	$139.10
Purchase #5	$151.34	11.256%	$168.3748	$168.37	$168.35	$168.40
Purchase #6	$100.50	7.153%	$107.6888	$107.69	$107.70	$107.70
Purchase #7	$12.56	10.132%	$13.8326	$13.83	$13.85	$13.80
7 purchase totals =	$971.94		$1,081.9341	$1,081.93	$1,082.00	$1,081.90