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	$98.51	5.505%	$103.933	$103.93	$103.95	$103.90
Purchase #2	$158.40	5.321%	$166.8285	$166.83	$166.85	$166.80
Purchase #3	$250.62	13.256%	$283.8422	$283.84	$283.85	$283.80
Purchase #4	$29.89	5.553%	$31.5498	$31.55	$31.55	$31.50
Purchase #5	$83.49	8.156%	$90.2994	$90.30	$90.30	$90.30
Purchase #6	$25.47	5.158%	$26.7837	$26.78	$26.80	$26.80
Purchase #7	$117.47	11.494%	$130.972	$130.97	$130.95	$131.00
7 purchase totals =	$763.85		$834.2086	$834.20	$834.25	$834.10