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	$115.98	7.785%	$125.009	$125.01	$125.00	$125.00
Purchase #2	$154.46	4.560%	$161.5034	$161.50	$161.50	$161.50
Purchase #3	$7.46	5.181%	$7.8465	$7.85	$7.85	$7.80
Purchase #4	$103.50	5.743%	$109.444	$109.44	$109.45	$109.40
Purchase #5	$125.59	12.312%	$141.0526	$141.05	$141.05	$141.10
Purchase #6	$31.59	6.754%	$33.7236	$33.72	$33.70	$33.70
Purchase #7	$128.70	9.766%	$141.2688	$141.27	$141.25	$141.30
7 purchase totals =	$667.28		$719.8479	$719.84	$719.80	$719.80