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	$47.80	7.583%	$51.4247	$51.42	$51.40	$51.40
Purchase #2	$168.58	9.738%	$184.9963	$185.00	$185.00	$185.00
Purchase #3	$220.89	3.390%	$228.3782	$228.38	$228.40	$228.40
Purchase #4	$209.81	7.568%	$225.6884	$225.69	$225.70	$225.70
Purchase #5	$132.53	13.824%	$150.8509	$150.85	$150.85	$150.90
Purchase #6	$151.46	8.850%	$164.8642	$164.86	$164.85	$164.90
Purchase #7	$216.50	11.542%	$241.4884	$241.49	$241.50	$241.50
7 purchase totals =	$1,147.57		$1,247.6911	$1,247.69	$1,247.70	$1,247.80