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	$70.43	9.177%	$76.8934	$76.89	$76.90	$76.90
Purchase #2	$208.47	6.629%	$222.2895	$222.29	$222.30	$222.30
Purchase #3	$236.53	8.360%	$256.3039	$256.30	$256.30	$256.30
Purchase #4	$213.71	9.507%	$234.0274	$234.03	$234.05	$234.00
Purchase #5	$85.31	7.486%	$91.6963	$91.70	$91.70	$91.70
Purchase #6	$41.78	6.580%	$44.5291	$44.53	$44.55	$44.50
Purchase #7	$90.73	9.480%	$99.3312	$99.33	$99.35	$99.30
7 purchase totals =	$946.96		$1,025.0708	$1,025.07	$1,025.15	$1,025.00