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	$30.57	13.224%	$34.6126	$34.61	$34.60	$34.60
Purchase #2	$30.97	8.278%	$33.5337	$33.53	$33.55	$33.50
Purchase #3	$30.38	3.719%	$31.5098	$31.51	$31.50	$31.50
Purchase #4	$40.48	7.187%	$43.3893	$43.39	$43.40	$43.40
Purchase #5	$208.81	7.765%	$225.0241	$225.02	$225.00	$225.00
Purchase #6	$93.30	11.446%	$103.9791	$103.98	$104.00	$104.00
Purchase #7	$26.28	13.687%	$29.8769	$29.88	$29.90	$29.90
7 purchase totals =	$460.79		$501.9255	$501.92	$501.95	$501.90