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	$131.39	4.707%	$137.5745	$137.57	$137.55	$137.60
Purchase #2	$11.59	6.574%	$12.3519	$12.35	$12.35	$12.40
Purchase #3	$6.89	11.704%	$7.6964	$7.70	$7.70	$7.70
Purchase #4	$40.88	8.240%	$44.2485	$44.25	$44.25	$44.20
Purchase #5	$213.65	4.594%	$223.4651	$223.47	$223.45	$223.50
Purchase #6	$136.85	7.588%	$147.2342	$147.23	$147.25	$147.20
Purchase #7	$154.39	7.221%	$165.5385	$165.54	$165.55	$165.50
7 purchase totals =	$695.64		$738.1091	$738.11	$738.10	$738.10