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	$132.60	6.586%	$141.333	$141.33	$141.35	$141.30
Purchase #2	$36.82	12.388%	$41.3813	$41.38	$41.40	$41.40
Purchase #3	$196.93	10.629%	$217.8617	$217.86	$217.85	$217.90
Purchase #4	$33.79	4.612%	$35.3484	$35.35	$35.35	$35.30
Purchase #5	$117.88	12.754%	$132.9144	$132.91	$132.90	$132.90
Purchase #6	$203.94	3.155%	$210.3743	$210.37	$210.35	$210.40
Purchase #7	$142.73	9.418%	$156.1723	$156.17	$156.15	$156.20
7 purchase totals =	$864.69		$935.3854	$935.37	$935.35	$935.40