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	$78.71	11.578%	$87.823	$87.82	$87.80	$87.80
Purchase #2	$107.45	4.811%	$112.6194	$112.62	$112.60	$112.60
Purchase #3	$11.89	11.121%	$13.2123	$13.21	$13.20	$13.20
Purchase #4	$53.79	11.348%	$59.8941	$59.89	$59.90	$59.90
Purchase #5	$131.88	4.545%	$137.8739	$137.87	$137.85	$137.90
Purchase #6	$114.81	4.511%	$119.9891	$119.99	$120.00	$120.00
Purchase #7	$164.47	9.453%	$180.0173	$180.02	$180.00	$180.00
7 purchase totals =	$663.00		$711.4291	$711.42	$711.35	$711.40