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	$118.59	4.451%	$123.8684	$123.87	$123.85	$123.90
Purchase #2	$30.59	6.273%	$32.5089	$32.51	$32.50	$32.50
Purchase #3	$43.97	13.776%	$50.0273	$50.03	$50.05	$50.00
Purchase #4	$231.90	11.610%	$258.8236	$258.82	$258.80	$258.80
Purchase #5	$44.82	4.550%	$46.8593	$46.86	$46.85	$46.90
Purchase #6	$143.62	9.336%	$157.0284	$157.03	$157.05	$157.00
Purchase #7	$122.35	3.614%	$126.7717	$126.77	$126.75	$126.80
7 purchase totals =	$735.84		$795.8876	$795.89	$795.85	$795.90