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	$160.97	6.315%	$171.1353	$171.14	$171.15	$171.10
Purchase #2	$59.33	3.244%	$61.2547	$61.25	$61.25	$61.30
Purchase #3	$34.59	9.774%	$37.9708	$37.97	$37.95	$38.00
Purchase #4	$69.88	9.316%	$76.39	$76.39	$76.40	$76.40
Purchase #5	$66.30	9.821%	$72.8113	$72.81	$72.80	$72.80
Purchase #6	$248.92	12.686%	$280.498	$280.50	$280.50	$280.50
Purchase #7	$241.88	10.146%	$266.4211	$266.42	$266.40	$266.40
7 purchase totals =	$881.87		$966.4812	$966.48	$966.45	$966.50