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	$110.70	5.244%	$116.5051	$116.51	$116.50	$116.50
Purchase #2	$174.86	8.682%	$190.0413	$190.04	$190.05	$190.00
Purchase #3	$53.78	13.401%	$60.9871	$60.99	$61.00	$61.00
Purchase #4	$178.82	9.762%	$196.2764	$196.28	$196.30	$196.30
Purchase #5	$140.94	8.620%	$153.089	$153.09	$153.10	$153.10
Purchase #6	$119.93	3.434%	$124.0484	$124.05	$124.05	$124.00
Purchase #7	$169.47	7.752%	$182.6073	$182.61	$182.60	$182.60
7 purchase totals =	$948.50		$1,023.5546	$1,023.57	$1,023.60	$1,023.50