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	$239.59	8.580%	$260.1468	$260.15	$260.15	$260.10
Purchase #2	$81.86	8.785%	$89.0514	$89.05	$89.05	$89.10
Purchase #3	$68.48	4.748%	$71.7314	$71.73	$71.75	$71.70
Purchase #4	$34.90	7.694%	$37.5852	$37.59	$37.60	$37.60
Purchase #5	$157.94	3.122%	$162.8709	$162.87	$162.85	$162.90
Purchase #6	$77.33	8.285%	$83.7368	$83.74	$83.75	$83.70
Purchase #7	$156.74	13.259%	$177.5222	$177.52	$177.50	$177.50
7 purchase totals =	$816.84		$882.6447	$882.65	$882.65	$882.60