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	$152.54	6.788%	$162.8944	$162.89	$162.90	$162.90
Purchase #2	$120.98	13.853%	$137.7394	$137.74	$137.75	$137.70
Purchase #3	$29.69	6.661%	$31.6677	$31.67	$31.65	$31.70
Purchase #4	$53.43	13.452%	$60.6174	$60.62	$60.60	$60.60
Purchase #5	$223.55	8.676%	$242.9452	$242.95	$242.95	$242.90
Purchase #6	$40.71	12.636%	$45.8541	$45.85	$45.85	$45.90
Purchase #7	$188.52	13.168%	$213.3443	$213.34	$213.35	$213.30
7 purchase totals =	$809.42		$895.0625	$895.06	$895.05	$895.00