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	$231.61	10.679%	$256.3436	$256.34	$256.35	$256.30
Purchase #2	$102.90	13.428%	$116.7174	$116.72	$116.70	$116.70
Purchase #3	$35.70	12.648%	$40.2153	$40.22	$40.20	$40.20
Purchase #4	$234.57	8.763%	$255.1254	$255.13	$255.15	$255.10
Purchase #5	$35.99	6.320%	$38.2646	$38.26	$38.25	$38.30
Purchase #6	$203.59	4.750%	$213.2605	$213.26	$213.25	$213.30
Purchase #7	$144.69	6.804%	$154.5347	$154.53	$154.55	$154.50
7 purchase totals =	$989.05		$1,074.4615	$1,074.46	$1,074.45	$1,074.40