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	$190.26	7.355%	$204.2536	$204.25	$204.25	$204.30
Purchase #2	$140.95	3.209%	$145.4731	$145.47	$145.45	$145.50
Purchase #3	$37.85	13.323%	$42.8928	$42.89	$42.90	$42.90
Purchase #4	$66.29	12.517%	$74.5875	$74.59	$74.60	$74.60
Purchase #5	$137.96	3.103%	$142.2409	$142.24	$142.25	$142.20
Purchase #6	$37.81	3.700%	$39.209	$39.21	$39.20	$39.20
Purchase #7	$225.52	12.546%	$253.8137	$253.81	$253.80	$253.80
7 purchase totals =	$836.64		$902.4706	$902.46	$902.45	$902.50