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	$74.94	9.257%	$81.8772	$81.88	$81.90	$81.90
Purchase #2	$119.34	3.527%	$123.5491	$123.55	$123.55	$123.50
Purchase #3	$53.37	8.756%	$58.0431	$58.04	$58.05	$58.00
Purchase #4	$88.99	7.419%	$95.5922	$95.59	$95.60	$95.60
Purchase #5	$140.67	7.846%	$151.707	$151.71	$151.70	$151.70
Purchase #6	$105.98	10.624%	$117.2393	$117.24	$117.25	$117.20
Purchase #7	$100.61	12.705%	$113.3925	$113.39	$113.40	$113.40
7 purchase totals =	$683.90		$741.4004	$741.40	$741.45	$741.30