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	$109.89	5.459%	$115.8889	$115.89	$115.90	$115.90
Purchase #2	$161.88	7.248%	$173.6131	$173.61	$173.60	$173.60
Purchase #3	$156.93	10.228%	$172.9808	$172.98	$173.00	$173.00
Purchase #4	$208.29	8.154%	$225.274	$225.27	$225.25	$225.30
Purchase #5	$172.47	7.795%	$185.914	$185.91	$185.90	$185.90
Purchase #6	$213.98	11.177%	$237.8965	$237.90	$237.90	$237.90
Purchase #7	$173.72	10.149%	$191.3508	$191.35	$191.35	$191.40
7 purchase totals =	$1,197.16		$1,302.9181	$1,302.91	$1,302.90	$1,303.00