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	$217.59	8.236%	$235.5107	$235.51	$235.50	$235.50
Purchase #2	$142.77	13.484%	$162.0211	$162.02	$162.00	$162.00
Purchase #3	$222.28	8.193%	$240.4914	$240.49	$240.50	$240.50
Purchase #4	$33.61	11.558%	$37.4946	$37.49	$37.50	$37.50
Purchase #5	$42.57	3.220%	$43.9408	$43.94	$43.95	$43.90
Purchase #6	$204.36	4.181%	$212.9043	$212.90	$212.90	$212.90
Purchase #7	$146.61	3.178%	$151.2693	$151.27	$151.25	$151.30
7 purchase totals =	$1,009.79		$1,083.6322	$1,083.62	$1,083.60	$1,083.60