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	$150.33	3.680%	$155.8621	$155.86	$155.85	$155.90
Purchase #2	$123.74	7.309%	$132.7842	$132.78	$132.80	$132.80
Purchase #3	$12.31	12.399%	$13.8363	$13.84	$13.85	$13.80
Purchase #4	$107.82	5.222%	$113.4504	$113.45	$113.45	$113.50
Purchase #5	$142.38	8.743%	$154.8283	$154.83	$154.85	$154.80
Purchase #6	$50.33	12.673%	$56.7083	$56.71	$56.70	$56.70
Purchase #7	$120.90	13.540%	$137.2699	$137.27	$137.25	$137.30
7 purchase totals =	$707.81		$764.7395	$764.74	$764.75	$764.80