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	$42.45	3.242%	$43.8262	$43.83	$43.85	$43.80
Purchase #2	$143.57	10.125%	$158.1065	$158.11	$158.10	$158.10
Purchase #3	$247.28	5.476%	$260.8211	$260.82	$260.80	$260.80
Purchase #4	$129.25	5.599%	$136.4867	$136.49	$136.50	$136.50
Purchase #5	$135.89	6.138%	$144.2309	$144.23	$144.25	$144.20
Purchase #6	$129.86	10.741%	$143.8083	$143.81	$143.80	$143.80
Purchase #7	$114.72	9.282%	$125.3683	$125.37	$125.35	$125.40
7 purchase totals =	$943.02		$1,012.6480	$1,012.66	$1,012.65	$1,012.60