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	$57.47	8.222%	$62.1952	$62.20	$62.20	$62.20
Purchase #2	$76.99	11.166%	$85.5867	$85.59	$85.60	$85.60
Purchase #3	$59.34	12.692%	$66.8714	$66.87	$66.85	$66.90
Purchase #4	$9.90	6.659%	$10.5592	$10.56	$10.55	$10.60
Purchase #5	$78.25	5.134%	$82.2674	$82.27	$82.25	$82.30
Purchase #6	$242.33	13.158%	$274.2158	$274.22	$274.20	$274.20
Purchase #7	$61.98	11.256%	$68.9565	$68.96	$68.95	$69.00
7 purchase totals =	$586.26		$650.6522	$650.67	$650.60	$650.80