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	$76.41	6.520%	$81.3919	$81.39	$81.40	$81.40
Purchase #2	$126.38	13.317%	$143.21	$143.21	$143.20	$143.20
Purchase #3	$44.98	3.301%	$46.4648	$46.46	$46.45	$46.50
Purchase #4	$82.46	6.150%	$87.5313	$87.53	$87.55	$87.50
Purchase #5	$114.87	12.757%	$129.524	$129.52	$129.50	$129.50
Purchase #6	$174.94	12.217%	$196.3124	$196.31	$196.30	$196.30
Purchase #7	$32.39	10.405%	$35.7602	$35.76	$35.75	$35.80
7 purchase totals =	$652.43		$720.1946	$720.18	$720.15	$720.20