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	$113.70	8.862%	$123.7761	$123.78	$123.80	$123.80
Purchase #2	$109.25	9.209%	$119.3108	$119.31	$119.30	$119.30
Purchase #3	$125.50	9.416%	$137.3171	$137.32	$137.30	$137.30
Purchase #4	$41.82	7.733%	$45.0539	$45.05	$45.05	$45.10
Purchase #5	$168.79	10.472%	$186.4657	$186.47	$186.45	$186.50
Purchase #6	$196.66	8.458%	$213.2935	$213.29	$213.30	$213.30
Purchase #7	$60.31	11.601%	$67.3066	$67.31	$67.30	$67.30
7 purchase totals =	$816.03		$892.5237	$892.53	$892.50	$892.60