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	$97.54	8.634%	$105.9616	$105.96	$105.95	$106.00
Purchase #2	$114.51	3.487%	$118.503	$118.50	$118.50	$118.50
Purchase #3	$128.74	12.662%	$145.0411	$145.04	$145.05	$145.00
Purchase #4	$20.54	8.224%	$22.2292	$22.23	$22.25	$22.20
Purchase #5	$212.46	13.383%	$240.8935	$240.89	$240.90	$240.90
Purchase #6	$69.37	4.468%	$72.4695	$72.47	$72.45	$72.50
Purchase #7	$105.42	10.319%	$116.2983	$116.30	$116.30	$116.30
7 purchase totals =	$748.58		$821.3962	$821.39	$821.40	$821.40