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	$63.46	7.842%	$68.4365	$68.44	$68.45	$68.40
Purchase #2	$22.46	10.605%	$24.8419	$24.84	$24.85	$24.80
Purchase #3	$56.91	4.692%	$59.5802	$59.58	$59.60	$59.60
Purchase #4	$56.98	4.124%	$59.3299	$59.33	$59.35	$59.30
Purchase #5	$210.54	6.629%	$224.4967	$224.50	$224.50	$224.50
Purchase #6	$241.38	13.676%	$274.3911	$274.39	$274.40	$274.40
Purchase #7	$58.90	7.786%	$63.486	$63.49	$63.50	$63.50
7 purchase totals =	$710.63		$774.5623	$774.57	$774.65	$774.50