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	$63.32	13.625%	$71.9474	$71.95	$71.95	$71.90
Purchase #2	$141.32	8.287%	$153.0312	$153.03	$153.05	$153.00
Purchase #3	$83.27	9.136%	$90.8775	$90.88	$90.90	$90.90
Purchase #4	$223.47	10.754%	$247.502	$247.50	$247.50	$247.50
Purchase #5	$221.37	10.648%	$244.9415	$244.94	$244.95	$244.90
Purchase #6	$227.25	8.562%	$246.7071	$246.71	$246.70	$246.70
Purchase #7	$63.91	7.326%	$68.592	$68.59	$68.60	$68.60
7 purchase totals =	$1,023.91		$1,123.5987	$1,123.60	$1,123.65	$1,123.50