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	$136.95	3.192%	$141.3214	$141.32	$141.30	$141.30
Purchase #2	$139.71	3.488%	$144.5831	$144.58	$144.60	$144.60
Purchase #3	$112.80	11.564%	$125.8442	$125.84	$125.85	$125.80
Purchase #4	$105.38	10.480%	$116.4238	$116.42	$116.40	$116.40
Purchase #5	$55.89	11.463%	$62.2967	$62.30	$62.30	$62.30
Purchase #6	$176.29	4.466%	$184.1631	$184.16	$184.15	$184.20
Purchase #7	$21.48	6.541%	$22.885	$22.89	$22.90	$22.90
7 purchase totals =	$748.50		$797.5173	$797.51	$797.50	$797.50