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	$48.48	4.287%	$50.5583	$50.56	$50.55	$50.60
Purchase #2	$159.72	5.811%	$169.0013	$169.00	$169.00	$169.00
Purchase #3	$77.31	10.868%	$85.7121	$85.71	$85.70	$85.70
Purchase #4	$217.50	11.495%	$242.5016	$242.50	$242.50	$242.50
Purchase #5	$204.32	8.234%	$221.1437	$221.14	$221.15	$221.10
Purchase #6	$242.59	8.369%	$262.8924	$262.89	$262.90	$262.90
Purchase #7	$132.67	7.440%	$142.5406	$142.54	$142.55	$142.50
7 purchase totals =	$1,082.59		$1,174.3500	$1,174.34	$1,174.35	$1,174.30