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	$68.90	7.550%	$74.102	$74.10	$74.10	$74.10
Purchase #2	$36.78	11.291%	$40.9328	$40.93	$40.95	$40.90
Purchase #3	$78.76	13.105%	$89.0815	$89.08	$89.10	$89.10
Purchase #4	$32.52	3.117%	$33.5336	$33.53	$33.55	$33.50
Purchase #5	$27.55	10.469%	$30.4342	$30.43	$30.45	$30.40
Purchase #6	$169.52	12.624%	$190.9202	$190.92	$190.90	$190.90
Purchase #7	$88.74	5.741%	$93.8346	$93.83	$93.85	$93.80
7 purchase totals =	$502.77		$552.8389	$552.82	$552.90	$552.70