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	$56.68	8.457%	$61.4734	$61.47	$61.45	$61.50
Purchase #2	$37.49	7.569%	$40.3276	$40.33	$40.35	$40.30
Purchase #3	$80.93	6.867%	$86.4875	$86.49	$86.50	$86.50
Purchase #4	$57.70	13.153%	$65.2893	$65.29	$65.30	$65.30
Purchase #5	$247.34	7.600%	$266.1378	$266.14	$266.15	$266.10
Purchase #6	$219.82	9.653%	$241.0392	$241.04	$241.05	$241.00
Purchase #7	$62.25	6.808%	$66.488	$66.49	$66.50	$66.50
7 purchase totals =	$762.21		$827.2428	$827.25	$827.30	$827.20