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	$53.56	12.438%	$60.2218	$60.22	$60.20	$60.20
Purchase #2	$43.91	4.276%	$45.7876	$45.79	$45.80	$45.80
Purchase #3	$17.59	13.188%	$19.9098	$19.91	$19.90	$19.90
Purchase #4	$178.66	3.486%	$184.8881	$184.89	$184.90	$184.90
Purchase #5	$246.74	11.410%	$274.893	$274.89	$274.90	$274.90
Purchase #6	$239.81	13.664%	$272.5776	$272.58	$272.60	$272.60
Purchase #7	$206.72	7.794%	$222.8318	$222.83	$222.85	$222.80
7 purchase totals =	$986.99		$1,081.1097	$1,081.11	$1,081.15	$1,081.10