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	$132.97	9.308%	$145.3468	$145.35	$145.35	$145.30
Purchase #2	$201.37	11.750%	$225.031	$225.03	$225.05	$225.00
Purchase #3	$131.68	7.125%	$141.0622	$141.06	$141.05	$141.10
Purchase #4	$113.77	13.137%	$128.716	$128.72	$128.70	$128.70
Purchase #5	$32.79	3.460%	$33.9245	$33.92	$33.90	$33.90
Purchase #6	$127.40	12.873%	$143.8002	$143.80	$143.80	$143.80
Purchase #7	$39.59	7.770%	$42.6661	$42.67	$42.65	$42.70
7 purchase totals =	$779.57		$860.5468	$860.55	$860.50	$860.50