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	$63.98	5.298%	$67.3697	$67.37	$67.35	$67.40
Purchase #2	$158.37	9.794%	$173.8808	$173.88	$173.90	$173.90
Purchase #3	$145.64	9.178%	$159.0068	$159.01	$159.00	$159.00
Purchase #4	$246.90	12.602%	$278.0143	$278.01	$278.00	$278.00
Purchase #5	$132.57	12.226%	$148.778	$148.78	$148.80	$148.80
Purchase #6	$71.79	9.246%	$78.4277	$78.43	$78.45	$78.40
Purchase #7	$25.64	3.121%	$26.4402	$26.44	$26.45	$26.40
7 purchase totals =	$844.89		$931.9175	$931.92	$931.95	$931.90