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	$194.95	11.266%	$216.9131	$216.91	$216.90	$216.90
Purchase #2	$111.25	10.243%	$122.6453	$122.65	$122.65	$122.60
Purchase #3	$225.83	10.823%	$250.2716	$250.27	$250.25	$250.30
Purchase #4	$128.32	13.857%	$146.1013	$146.10	$146.10	$146.10
Purchase #5	$38.47	5.340%	$40.5243	$40.52	$40.50	$40.50
Purchase #6	$6.43	10.756%	$7.1216	$7.12	$7.10	$7.10
Purchase #7	$5.56	4.674%	$5.8199	$5.82	$5.80	$5.80
7 purchase totals =	$710.81		$789.3971	$789.39	$789.30	$789.30