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	$231.47	13.434%	$262.5657	$262.57	$262.55	$262.60
Purchase #2	$37.68	8.630%	$40.9318	$40.93	$40.95	$40.90
Purchase #3	$82.42	6.234%	$87.5581	$87.56	$87.55	$87.60
Purchase #4	$158.31	6.829%	$169.121	$169.12	$169.10	$169.10
Purchase #5	$186.53	7.144%	$199.8557	$199.86	$199.85	$199.90
Purchase #6	$184.55	3.221%	$190.4944	$190.49	$190.50	$190.50
Purchase #7	$78.77	13.653%	$89.5245	$89.52	$89.50	$89.50
7 purchase totals =	$959.73		$1,040.0512	$1,040.05	$1,040.00	$1,040.10