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	$31.58	13.394%	$35.8098	$35.81	$35.80	$35.80
Purchase #2	$216.57	10.144%	$238.5389	$238.54	$238.55	$238.50
Purchase #3	$99.26	12.571%	$111.738	$111.74	$111.75	$111.70
Purchase #4	$140.39	4.806%	$147.1371	$147.14	$147.15	$147.10
Purchase #5	$201.59	4.427%	$210.5144	$210.51	$210.50	$210.50
Purchase #6	$217.53	7.504%	$233.8535	$233.85	$233.85	$233.90
Purchase #7	$112.45	8.506%	$122.015	$122.02	$122.00	$122.00
7 purchase totals =	$1,019.37		$1,099.6067	$1,099.61	$1,099.60	$1,099.50