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	$183.33	7.717%	$197.4776	$197.48	$197.50	$197.50
Purchase #2	$38.32	4.279%	$39.9597	$39.96	$39.95	$40.00
Purchase #3	$164.89	12.493%	$185.4897	$185.49	$185.50	$185.50
Purchase #4	$138.74	3.452%	$143.5293	$143.53	$143.55	$143.50
Purchase #5	$30.92	13.652%	$35.1412	$35.14	$35.15	$35.10
Purchase #6	$42.96	5.341%	$45.2545	$45.25	$45.25	$45.30
Purchase #7	$101.64	10.213%	$112.0205	$112.02	$112.00	$112.00
7 purchase totals =	$700.80		$758.8725	$758.87	$758.90	$758.90