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	$51.75	11.347%	$57.6221	$57.62	$57.60	$57.60
Purchase #2	$202.89	7.355%	$217.8126	$217.81	$217.80	$217.80
Purchase #3	$216.70	13.418%	$245.7768	$245.78	$245.80	$245.80
Purchase #4	$66.61	6.593%	$71.0016	$71.00	$71.00	$71.00
Purchase #5	$102.51	11.102%	$113.8907	$113.89	$113.90	$113.90
Purchase #6	$129.32	11.644%	$144.378	$144.38	$144.40	$144.40
Purchase #7	$103.91	7.472%	$111.6742	$111.67	$111.65	$111.70
7 purchase totals =	$873.69		$962.1560	$962.15	$962.15	$962.20