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	$104.62	6.759%	$111.6913	$111.69	$111.70	$111.70
Purchase #2	$90.78	12.472%	$102.1021	$102.10	$102.10	$102.10
Purchase #3	$36.32	10.596%	$40.1685	$40.17	$40.15	$40.20
Purchase #4	$162.46	12.273%	$182.3987	$182.40	$182.40	$182.40
Purchase #5	$194.78	8.843%	$212.0044	$212.00	$212.00	$212.00
Purchase #6	$119.85	12.365%	$134.6695	$134.67	$134.65	$134.70
Purchase #7	$169.90	9.691%	$186.365	$186.37	$186.35	$186.40
7 purchase totals =	$878.71		$969.3995	$969.40	$969.35	$969.50