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	$202.59	6.738%	$216.2405	$216.24	$216.25	$216.20
Purchase #2	$20.60	5.763%	$21.7872	$21.79	$21.80	$21.80
Purchase #3	$93.51	13.258%	$105.9076	$105.91	$105.90	$105.90
Purchase #4	$72.25	12.792%	$81.4922	$81.49	$81.50	$81.50
Purchase #5	$238.41	4.376%	$248.8428	$248.84	$248.85	$248.80
Purchase #6	$127.53	11.468%	$142.1551	$142.16	$142.15	$142.20
Purchase #7	$190.38	7.682%	$205.005	$205.01	$205.00	$205.00
7 purchase totals =	$945.27		$1,021.4304	$1,021.44	$1,021.45	$1,021.40