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	$9.77	7.112%	$10.4648	$10.46	$10.45	$10.50
Purchase #2	$69.78	11.792%	$78.0085	$78.01	$78.00	$78.00
Purchase #3	$187.71	6.863%	$200.5925	$200.59	$200.60	$200.60
Purchase #4	$145.37	5.736%	$153.7084	$153.71	$153.70	$153.70
Purchase #5	$31.48	6.309%	$33.4661	$33.47	$33.45	$33.50
Purchase #6	$37.72	6.517%	$40.1782	$40.18	$40.20	$40.20
Purchase #7	$167.55	9.772%	$183.923	$183.92	$183.90	$183.90
7 purchase totals =	$649.38		$700.3415	$700.34	$700.30	$700.40