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	$239.48	7.258%	$256.8615	$256.86	$256.85	$256.90
Purchase #2	$36.57	12.330%	$41.0791	$41.08	$41.10	$41.10
Purchase #3	$50.97	3.536%	$52.7723	$52.77	$52.75	$52.80
Purchase #4	$42.34	7.521%	$45.5244	$45.52	$45.50	$45.50
Purchase #5	$89.51	9.566%	$98.0725	$98.07	$98.05	$98.10
Purchase #6	$226.73	5.277%	$238.6945	$238.69	$238.70	$238.70
Purchase #7	$105.85	8.267%	$114.6006	$114.60	$114.60	$114.60
7 purchase totals =	$791.45		$847.6049	$847.59	$847.55	$847.70