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	$125.46	13.156%	$141.9655	$141.97	$141.95	$142.00
Purchase #2	$139.38	7.828%	$150.2907	$150.29	$150.30	$150.30
Purchase #3	$103.56	6.804%	$110.6062	$110.61	$110.60	$110.60
Purchase #4	$158.77	10.285%	$175.0995	$175.10	$175.10	$175.10
Purchase #5	$78.61	8.438%	$85.2431	$85.24	$85.25	$85.20
Purchase #6	$22.74	6.604%	$24.2417	$24.24	$24.25	$24.20
Purchase #7	$34.52	9.803%	$37.904	$37.90	$37.90	$37.90
7 purchase totals =	$663.04		$725.3507	$725.35	$725.35	$725.30