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	$21.52	11.744%	$24.0473	$24.05	$24.05	$24.00
Purchase #2	$34.91	7.729%	$37.6082	$37.61	$37.60	$37.60
Purchase #3	$200.52	6.674%	$213.9027	$213.90	$213.90	$213.90
Purchase #4	$225.25	13.515%	$255.6925	$255.69	$255.70	$255.70
Purchase #5	$100.47	13.696%	$114.2304	$114.23	$114.25	$114.20
Purchase #6	$140.46	10.332%	$154.9723	$154.97	$154.95	$155.00
Purchase #7	$88.45	11.772%	$98.8623	$98.86	$98.85	$98.90
7 purchase totals =	$811.58		$899.3157	$899.31	$899.30	$899.30