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	$78.93	13.165%	$89.3211	$89.32	$89.30	$89.30
Purchase #2	$194.54	12.246%	$218.3634	$218.36	$218.35	$218.40
Purchase #3	$41.59	11.248%	$46.268	$46.27	$46.25	$46.30
Purchase #4	$162.77	6.808%	$173.8514	$173.85	$173.85	$173.90
Purchase #5	$136.57	7.677%	$147.0545	$147.05	$147.05	$147.10
Purchase #6	$97.95	6.808%	$104.6184	$104.62	$104.60	$104.60
Purchase #7	$143.39	8.252%	$155.2225	$155.22	$155.20	$155.20
7 purchase totals =	$855.74		$934.6993	$934.69	$934.60	$934.80