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	$244.81	12.520%	$275.4602	$275.46	$275.45	$275.50
Purchase #2	$144.35	4.678%	$151.1027	$151.10	$151.10	$151.10
Purchase #3	$225.47	4.802%	$236.2971	$236.30	$236.30	$236.30
Purchase #4	$72.38	4.317%	$75.5046	$75.50	$75.50	$75.50
Purchase #5	$228.87	4.379%	$238.8922	$238.89	$238.90	$238.90
Purchase #6	$98.96	10.873%	$109.7199	$109.72	$109.70	$109.70
Purchase #7	$199.49	8.431%	$216.309	$216.31	$216.30	$216.30
7 purchase totals =	$1,214.33		$1,303.2857	$1,303.28	$1,303.25	$1,303.30