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	$7.29	4.322%	$7.6051	$7.61	$7.60	$7.60
Purchase #2	$224.94	13.594%	$255.5183	$255.52	$255.50	$255.50
Purchase #3	$73.61	12.703%	$82.9607	$82.96	$82.95	$83.00
Purchase #4	$101.74	12.156%	$114.1075	$114.11	$114.10	$114.10
Purchase #5	$40.42	5.252%	$42.5429	$42.54	$42.55	$42.50
Purchase #6	$182.98	5.181%	$192.4602	$192.46	$192.45	$192.50
Purchase #7	$6.91	3.519%	$7.1532	$7.15	$7.15	$7.20
7 purchase totals =	$637.89		$702.3479	$702.35	$702.30	$702.40