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	$38.45	11.691%	$42.9452	$42.95	$42.95	$42.90
Purchase #2	$111.56	13.508%	$126.6295	$126.63	$126.65	$126.60
Purchase #3	$246.57	7.663%	$265.4647	$265.46	$265.45	$265.50
Purchase #4	$176.73	11.788%	$197.5629	$197.56	$197.55	$197.60
Purchase #5	$118.79	10.735%	$131.5421	$131.54	$131.55	$131.50
Purchase #6	$104.42	13.243%	$118.2483	$118.25	$118.25	$118.20
Purchase #7	$180.93	7.796%	$195.0353	$195.04	$195.05	$195.00
7 purchase totals =	$977.45		$1,077.4280	$1,077.43	$1,077.45	$1,077.30