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	$41.86	10.487%	$46.2499	$46.25	$46.25	$46.20
Purchase #2	$116.63	12.387%	$131.077	$131.08	$131.10	$131.10
Purchase #3	$196.76	6.785%	$210.1102	$210.11	$210.10	$210.10
Purchase #4	$154.34	4.166%	$160.7698	$160.77	$160.75	$160.80
Purchase #5	$119.55	10.421%	$132.0083	$132.01	$132.00	$132.00
Purchase #6	$72.81	13.432%	$82.5898	$82.59	$82.60	$82.60
Purchase #7	$24.55	12.691%	$27.6656	$27.67	$27.65	$27.70
7 purchase totals =	$726.50		$790.4706	$790.48	$790.45	$790.50