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	$184.45	3.817%	$191.4905	$191.49	$191.50	$191.50
Purchase #2	$124.87	12.125%	$140.0105	$140.01	$140.00	$140.00
Purchase #3	$37.47	3.722%	$38.8646	$38.86	$38.85	$38.90
Purchase #4	$133.45	4.402%	$139.3245	$139.32	$139.30	$139.30
Purchase #5	$146.58	6.385%	$155.9391	$155.94	$155.95	$155.90
Purchase #6	$109.97	8.419%	$119.2284	$119.23	$119.25	$119.20
Purchase #7	$79.84	13.829%	$90.8811	$90.88	$90.90	$90.90
7 purchase totals =	$816.63		$875.7387	$875.73	$875.75	$875.70