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	$29.52	7.669%	$31.7839	$31.78	$31.80	$31.80
Purchase #2	$13.48	10.287%	$14.8667	$14.87	$14.85	$14.90
Purchase #3	$39.69	13.483%	$45.0414	$45.04	$45.05	$45.00
Purchase #4	$217.29	7.414%	$233.3999	$233.40	$233.40	$233.40
Purchase #5	$233.66	11.102%	$259.6009	$259.60	$259.60	$259.60
Purchase #6	$46.86	12.102%	$52.531	$52.53	$52.55	$52.50
Purchase #7	$91.60	6.152%	$97.2352	$97.24	$97.25	$97.20
7 purchase totals =	$672.10		$734.4590	$734.46	$734.50	$734.40