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	$81.55	4.404%	$85.1415	$85.14	$85.15	$85.10
Purchase #2	$189.37	10.296%	$208.8675	$208.87	$208.85	$208.90
Purchase #3	$80.61	8.777%	$87.6851	$87.69	$87.70	$87.70
Purchase #4	$228.68	13.468%	$259.4786	$259.48	$259.50	$259.50
Purchase #5	$213.78	5.391%	$225.3049	$225.30	$225.30	$225.30
Purchase #6	$231.49	12.620%	$260.704	$260.70	$260.70	$260.70
Purchase #7	$85.58	5.768%	$90.5163	$90.52	$90.50	$90.50
7 purchase totals =	$1,111.06		$1,217.6979	$1,217.70	$1,217.70	$1,217.70