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	$100.55	11.277%	$111.889	$111.89	$111.90	$111.90
Purchase #2	$206.58	6.505%	$220.018	$220.02	$220.00	$220.00
Purchase #3	$56.55	4.733%	$59.2265	$59.23	$59.25	$59.20
Purchase #4	$189.90	13.747%	$216.0056	$216.01	$216.00	$216.00
Purchase #5	$13.96	3.799%	$14.4903	$14.49	$14.50	$14.50
Purchase #6	$111.80	7.601%	$120.2979	$120.30	$120.30	$120.30
Purchase #7	$102.74	3.439%	$106.2732	$106.27	$106.25	$106.30
7 purchase totals =	$782.08		$848.2005	$848.21	$848.20	$848.20