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	$171.35	3.144%	$176.7372	$176.74	$176.75	$176.70
Purchase #2	$44.27	5.654%	$46.773	$46.77	$46.75	$46.80
Purchase #3	$37.78	13.313%	$42.8097	$42.81	$42.80	$42.80
Purchase #4	$73.88	6.363%	$78.581	$78.58	$78.60	$78.60
Purchase #5	$52.72	8.561%	$57.2334	$57.23	$57.25	$57.20
Purchase #6	$32.64	10.845%	$36.1798	$36.18	$36.20	$36.20
Purchase #7	$57.43	11.342%	$63.9437	$63.94	$63.95	$63.90
7 purchase totals =	$470.07		$502.2578	$502.25	$502.30	$502.20