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	$233.27	9.707%	$255.9135	$255.91	$255.90	$255.90
Purchase #2	$32.86	8.619%	$35.6922	$35.69	$35.70	$35.70
Purchase #3	$68.29	4.109%	$71.096	$71.10	$71.10	$71.10
Purchase #4	$247.48	5.141%	$260.2029	$260.20	$260.20	$260.20
Purchase #5	$19.50	5.582%	$20.5885	$20.59	$20.60	$20.60
Purchase #6	$207.90	13.742%	$236.4696	$236.47	$236.45	$236.50
Purchase #7	$167.84	13.155%	$189.9194	$189.92	$189.90	$189.90
7 purchase totals =	$977.14		$1,069.8821	$1,069.88	$1,069.85	$1,069.90