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	$110.56	5.456%	$116.5922	$116.59	$116.60	$116.60
Purchase #2	$227.49	4.464%	$237.6452	$237.65	$237.65	$237.60
Purchase #3	$110.46	6.590%	$117.7393	$117.74	$117.75	$117.70
Purchase #4	$230.54	13.503%	$261.6698	$261.67	$261.65	$261.70
Purchase #5	$37.62	8.756%	$40.914	$40.91	$40.90	$40.90
Purchase #6	$204.88	3.290%	$211.6206	$211.62	$211.60	$211.60
Purchase #7	$94.94	4.510%	$99.2218	$99.22	$99.20	$99.20
7 purchase totals =	$1,016.49		$1,085.4029	$1,085.40	$1,085.35	$1,085.30