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	$40.40	6.289%	$42.9408	$42.94	$42.95	$42.90
Purchase #2	$163.34	8.614%	$177.4101	$177.41	$177.40	$177.40
Purchase #3	$123.62	7.467%	$132.8507	$132.85	$132.85	$132.90
Purchase #4	$201.76	13.259%	$228.5114	$228.51	$228.50	$228.50
Purchase #5	$247.40	12.556%	$278.4635	$278.46	$278.45	$278.50
Purchase #6	$59.45	3.711%	$61.6562	$61.66	$61.65	$61.70
Purchase #7	$178.61	9.114%	$194.8885	$194.89	$194.90	$194.90
7 purchase totals =	$1,014.58		$1,116.7212	$1,116.72	$1,116.70	$1,116.80