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	$157.55	4.355%	$164.4113	$164.41	$164.40	$164.40
Purchase #2	$125.84	5.126%	$132.2906	$132.29	$132.30	$132.30
Purchase #3	$78.82	7.766%	$84.9412	$84.94	$84.95	$84.90
Purchase #4	$243.66	5.155%	$256.2207	$256.22	$256.20	$256.20
Purchase #5	$113.37	13.440%	$128.6069	$128.61	$128.60	$128.60
Purchase #6	$83.64	10.544%	$92.459	$92.46	$92.45	$92.50
Purchase #7	$58.54	13.748%	$66.5881	$66.59	$66.60	$66.60
7 purchase totals =	$861.42		$925.5178	$925.52	$925.50	$925.50