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	$132.40	12.222%	$148.5819	$148.58	$148.60	$148.60
Purchase #2	$182.74	13.480%	$207.3734	$207.37	$207.35	$207.40
Purchase #3	$126.83	10.760%	$140.4769	$140.48	$140.50	$140.50
Purchase #4	$29.43	11.241%	$32.7382	$32.74	$32.75	$32.70
Purchase #5	$122.63	12.174%	$137.559	$137.56	$137.55	$137.60
Purchase #6	$191.46	4.769%	$200.5907	$200.59	$200.60	$200.60
Purchase #7	$117.83	13.786%	$134.074	$134.07	$134.05	$134.10
7 purchase totals =	$903.32		$1,001.3941	$1,001.39	$1,001.40	$1,001.50