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	$83.75	12.366%	$94.1065	$94.11	$94.10	$94.10
Purchase #2	$29.59	9.605%	$32.4321	$32.43	$32.45	$32.40
Purchase #3	$122.45	7.404%	$131.5162	$131.52	$131.50	$131.50
Purchase #4	$145.69	9.564%	$159.6238	$159.62	$159.60	$159.60
Purchase #5	$144.60	7.773%	$155.8398	$155.84	$155.85	$155.80
Purchase #6	$225.48	11.480%	$251.3651	$251.37	$251.35	$251.40
Purchase #7	$246.39	10.402%	$272.0195	$272.02	$272.00	$272.00
7 purchase totals =	$997.95		$1,096.9030	$1,096.91	$1,096.85	$1,096.80