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	$94.90	13.610%	$107.8159	$107.82	$107.80	$107.80
Purchase #2	$95.88	3.475%	$99.2118	$99.21	$99.20	$99.20
Purchase #3	$127.70	6.768%	$136.3427	$136.34	$136.35	$136.30
Purchase #4	$108.49	7.381%	$116.4976	$116.50	$116.50	$116.50
Purchase #5	$7.71	13.196%	$8.7274	$8.73	$8.75	$8.70
Purchase #6	$39.81	10.161%	$43.8551	$43.86	$43.85	$43.90
Purchase #7	$91.93	9.741%	$100.8849	$100.88	$100.90	$100.90
7 purchase totals =	$566.42		$613.3354	$613.34	$613.35	$613.30