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	$213.78	6.196%	$227.0258	$227.03	$227.05	$227.00
Purchase #2	$44.48	7.315%	$47.7337	$47.73	$47.75	$47.70
Purchase #3	$54.32	4.219%	$56.6118	$56.61	$56.60	$56.60
Purchase #4	$140.76	7.534%	$151.3649	$151.36	$151.35	$151.40
Purchase #5	$39.67	6.526%	$42.2589	$42.26	$42.25	$42.30
Purchase #6	$70.67	11.135%	$78.5391	$78.54	$78.55	$78.50
Purchase #7	$55.84	5.351%	$58.828	$58.83	$58.85	$58.80
7 purchase totals =	$619.52		$662.3622	$662.36	$662.40	$662.30