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	$232.97	9.576%	$255.2792	$255.28	$255.30	$255.30
Purchase #2	$93.49	8.563%	$101.4955	$101.50	$101.50	$101.50
Purchase #3	$55.67	3.270%	$57.4904	$57.49	$57.50	$57.50
Purchase #4	$42.93	4.493%	$44.8588	$44.86	$44.85	$44.90
Purchase #5	$196.73	8.749%	$213.9419	$213.94	$213.95	$213.90
Purchase #6	$176.58	11.129%	$196.2316	$196.23	$196.25	$196.20
Purchase #7	$29.77	9.421%	$32.5746	$32.57	$32.55	$32.60
7 purchase totals =	$828.14		$901.8720	$901.87	$901.90	$901.90