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	$248.48	5.271%	$261.5774	$261.58	$261.60	$261.60
Purchase #2	$247.78	10.550%	$273.9208	$273.92	$273.90	$273.90
Purchase #3	$87.65	8.288%	$94.9144	$94.91	$94.90	$94.90
Purchase #4	$137.95	10.535%	$152.483	$152.48	$152.50	$152.50
Purchase #5	$73.91	6.514%	$78.7245	$78.72	$78.70	$78.70
Purchase #6	$10.47	13.685%	$11.9028	$11.90	$11.90	$11.90
Purchase #7	$116.87	10.197%	$128.7872	$128.79	$128.80	$128.80
7 purchase totals =	$923.11		$1,002.3101	$1,002.30	$1,002.30	$1,002.30