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	$64.50	3.429%	$66.7117	$66.71	$66.70	$66.70
Purchase #2	$15.32	10.360%	$16.9072	$16.91	$16.90	$16.90
Purchase #3	$147.97	13.651%	$168.1694	$168.17	$168.15	$168.20
Purchase #4	$57.95	3.245%	$59.8305	$59.83	$59.85	$59.80
Purchase #5	$33.92	9.131%	$37.0172	$37.02	$37.00	$37.00
Purchase #6	$32.97	3.695%	$34.1882	$34.19	$34.20	$34.20
Purchase #7	$88.75	6.528%	$94.5436	$94.54	$94.55	$94.50
7 purchase totals =	$441.38		$477.3678	$477.37	$477.35	$477.30