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	$48.89	5.189%	$51.4269	$51.43	$51.45	$51.40
Purchase #2	$51.42	6.308%	$54.6636	$54.66	$54.65	$54.70
Purchase #3	$156.86	5.513%	$165.5077	$165.51	$165.50	$165.50
Purchase #4	$200.45	11.654%	$223.8104	$223.81	$223.80	$223.80
Purchase #5	$211.81	12.374%	$238.0194	$238.02	$238.00	$238.00
Purchase #6	$144.35	4.459%	$150.7866	$150.79	$150.80	$150.80
Purchase #7	$230.54	8.748%	$250.7076	$250.71	$250.70	$250.70
7 purchase totals =	$1,044.32		$1,134.9222	$1,134.93	$1,134.90	$1,134.90