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	$237.52	7.169%	$254.5478	$254.55	$254.55	$254.50
Purchase #2	$248.65	4.552%	$259.9685	$259.97	$259.95	$260.00
Purchase #3	$51.84	7.213%	$55.5792	$55.58	$55.60	$55.60
Purchase #4	$238.28	13.692%	$270.9053	$270.91	$270.90	$270.90
Purchase #5	$116.38	12.215%	$130.5958	$130.60	$130.60	$130.60
Purchase #6	$83.39	8.507%	$90.484	$90.48	$90.50	$90.50
Purchase #7	$224.58	6.227%	$238.5646	$238.56	$238.55	$238.60
7 purchase totals =	$1,200.64		$1,300.6452	$1,300.65	$1,300.65	$1,300.70