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	$201.44	6.859%	$215.2568	$215.26	$215.25	$215.30
Purchase #2	$84.49	7.502%	$90.8284	$90.83	$90.85	$90.80
Purchase #3	$89.67	12.142%	$100.5577	$100.56	$100.55	$100.60
Purchase #4	$104.79	6.249%	$111.3383	$111.34	$111.35	$111.30
Purchase #5	$58.63	10.593%	$64.8407	$64.84	$64.85	$64.80
Purchase #6	$158.58	10.670%	$175.5005	$175.50	$175.50	$175.50
Purchase #7	$180.83	12.792%	$203.9618	$203.96	$203.95	$204.00
7 purchase totals =	$878.43		$962.2842	$962.29	$962.30	$962.30