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	$110.89	11.692%	$123.8553	$123.86	$123.85	$123.90
Purchase #2	$209.48	3.592%	$217.0045	$217.00	$217.00	$217.00
Purchase #3	$246.59	4.847%	$258.5422	$258.54	$258.55	$258.50
Purchase #4	$38.99	4.745%	$40.8401	$40.84	$40.85	$40.80
Purchase #5	$161.59	3.645%	$167.48	$167.48	$167.50	$167.50
Purchase #6	$159.38	5.144%	$167.5785	$167.58	$167.60	$167.60
Purchase #7	$244.70	5.762%	$258.7996	$258.80	$258.80	$258.80
7 purchase totals =	$1,171.62		$1,234.1002	$1,234.10	$1,234.15	$1,234.10