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	$106.55	6.295%	$113.2573	$113.26	$113.25	$113.30
Purchase #2	$85.66	11.694%	$95.6771	$95.68	$95.70	$95.70
Purchase #3	$16.26	13.711%	$18.4894	$18.49	$18.50	$18.50
Purchase #4	$122.85	12.153%	$137.78	$137.78	$137.80	$137.80
Purchase #5	$11.25	13.610%	$12.7811	$12.78	$12.80	$12.80
Purchase #6	$154.78	11.486%	$172.558	$172.56	$172.55	$172.60
Purchase #7	$208.31	11.265%	$231.7761	$231.78	$231.80	$231.80
7 purchase totals =	$705.66		$782.3190	$782.33	$782.40	$782.50