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	$141.77	4.772%	$148.5353	$148.54	$148.55	$148.50
Purchase #2	$69.90	4.303%	$72.9078	$72.91	$72.90	$72.90
Purchase #3	$107.88	10.353%	$119.0488	$119.05	$119.05	$119.00
Purchase #4	$125.85	10.536%	$139.1096	$139.11	$139.10	$139.10
Purchase #5	$154.78	10.206%	$170.5768	$170.58	$170.60	$170.60
Purchase #6	$134.95	11.252%	$150.1346	$150.13	$150.15	$150.10
Purchase #7	$185.67	12.403%	$208.6987	$208.70	$208.70	$208.70
7 purchase totals =	$920.80		$1,009.0116	$1,009.02	$1,009.05	$1,008.90