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	$162.52	12.179%	$182.3133	$182.31	$182.30	$182.30
Purchase #2	$162.48	12.597%	$182.9476	$182.95	$182.95	$182.90
Purchase #3	$114.66	13.787%	$130.4682	$130.47	$130.45	$130.50
Purchase #4	$182.44	3.856%	$189.4749	$189.47	$189.45	$189.50
Purchase #5	$50.38	7.608%	$54.2129	$54.21	$54.20	$54.20
Purchase #6	$12.51	7.485%	$13.4464	$13.45	$13.45	$13.40
Purchase #7	$116.82	11.412%	$130.1515	$130.15	$130.15	$130.20
7 purchase totals =	$801.81		$883.0148	$883.01	$882.95	$883.00