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	$227.96	6.351%	$242.4377	$242.44	$242.45	$242.40
Purchase #2	$36.41	8.453%	$39.4877	$39.49	$39.50	$39.50
Purchase #3	$11.82	13.244%	$13.3854	$13.39	$13.40	$13.40
Purchase #4	$19.54	8.329%	$21.1675	$21.17	$21.15	$21.20
Purchase #5	$163.63	13.147%	$185.1424	$185.14	$185.15	$185.10
Purchase #6	$221.47	7.815%	$238.7779	$238.78	$238.80	$238.80
Purchase #7	$143.34	3.756%	$148.7239	$148.72	$148.70	$148.70
7 purchase totals =	$824.17		$889.1225	$889.13	$889.15	$889.10