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	$220.79	9.581%	$241.9439	$241.94	$241.95	$241.90
Purchase #2	$88.37	13.368%	$100.1833	$100.18	$100.20	$100.20
Purchase #3	$91.44	13.701%	$103.9682	$103.97	$103.95	$104.00
Purchase #4	$248.61	7.348%	$266.8779	$266.88	$266.90	$266.90
Purchase #5	$250.77	4.785%	$262.7693	$262.77	$262.75	$262.80
Purchase #6	$50.90	3.828%	$52.8485	$52.85	$52.85	$52.80
Purchase #7	$109.76	7.150%	$117.6078	$117.61	$117.60	$117.60
7 purchase totals =	$1,060.64		$1,146.1989	$1,146.20	$1,146.20	$1,146.20