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	$94.50	12.754%	$106.5525	$106.55	$106.55	$106.60
Purchase #2	$135.34	3.727%	$140.3841	$140.38	$140.40	$140.40
Purchase #3	$126.85	11.385%	$141.2919	$141.29	$141.30	$141.30
Purchase #4	$54.91	8.817%	$59.7514	$59.75	$59.75	$59.80
Purchase #5	$221.66	7.653%	$238.6236	$238.62	$238.60	$238.60
Purchase #6	$100.33	7.514%	$107.8688	$107.87	$107.85	$107.90
Purchase #7	$221.34	13.821%	$251.9314	$251.93	$251.95	$251.90
7 purchase totals =	$954.93		$1,046.4037	$1,046.39	$1,046.40	$1,046.50