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	$136.53	12.419%	$153.4857	$153.49	$153.50	$153.50
Purchase #2	$140.89	10.790%	$156.092	$156.09	$156.10	$156.10
Purchase #3	$209.96	13.208%	$237.6915	$237.69	$237.70	$237.70
Purchase #4	$238.52	12.290%	$267.8341	$267.83	$267.85	$267.80
Purchase #5	$99.70	3.723%	$103.4118	$103.41	$103.40	$103.40
Purchase #6	$74.81	3.635%	$77.5293	$77.53	$77.55	$77.50
Purchase #7	$139.60	4.272%	$145.5637	$145.56	$145.55	$145.60
7 purchase totals =	$1,040.01		$1,141.6081	$1,141.60	$1,141.65	$1,141.60