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	$163.64	12.770%	$184.5368	$184.54	$184.55	$184.50
Purchase #2	$182.85	7.677%	$196.8874	$196.89	$196.90	$196.90
Purchase #3	$228.78	13.678%	$260.0725	$260.07	$260.05	$260.10
Purchase #4	$56.94	7.784%	$61.3722	$61.37	$61.35	$61.40
Purchase #5	$16.39	12.495%	$18.4379	$18.44	$18.45	$18.40
Purchase #6	$22.25	11.191%	$24.74	$24.74	$24.75	$24.70
Purchase #7	$17.64	3.404%	$18.2405	$18.24	$18.25	$18.20
7 purchase totals =	$688.49		$764.2873	$764.29	$764.30	$764.20