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	$68.87	6.689%	$73.4767	$73.48	$73.50	$73.50
Purchase #2	$72.30	7.377%	$77.6336	$77.63	$77.65	$77.60
Purchase #3	$151.43	9.534%	$165.8673	$165.87	$165.85	$165.90
Purchase #4	$240.94	7.443%	$258.8732	$258.87	$258.85	$258.90
Purchase #5	$33.39	7.331%	$35.8378	$35.84	$35.85	$35.80
Purchase #6	$10.90	11.680%	$12.1731	$12.17	$12.15	$12.20
Purchase #7	$88.45	7.833%	$95.3783	$95.38	$95.40	$95.40
7 purchase totals =	$666.28		$719.2400	$719.24	$719.25	$719.30