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	$81.78	8.787%	$88.966	$88.97	$88.95	$89.00
Purchase #2	$75.29	13.837%	$85.7079	$85.71	$85.70	$85.70
Purchase #3	$91.90	3.628%	$95.2341	$95.23	$95.25	$95.20
Purchase #4	$139.96	7.301%	$150.1785	$150.18	$150.20	$150.20
Purchase #5	$29.65	13.716%	$33.7168	$33.72	$33.70	$33.70
Purchase #6	$220.93	8.763%	$240.2901	$240.29	$240.30	$240.30
Purchase #7	$36.55	10.720%	$40.4682	$40.47	$40.45	$40.50
7 purchase totals =	$676.06		$734.5616	$734.57	$734.55	$734.60