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	$208.53	7.333%	$223.8215	$223.82	$223.80	$223.80
Purchase #2	$221.78	11.115%	$246.4308	$246.43	$246.45	$246.40
Purchase #3	$168.72	4.386%	$176.1201	$176.12	$176.10	$176.10
Purchase #4	$65.61	10.817%	$72.707	$72.71	$72.70	$72.70
Purchase #5	$139.92	5.153%	$147.1301	$147.13	$147.15	$147.10
Purchase #6	$126.36	13.440%	$143.3428	$143.34	$143.35	$143.30
Purchase #7	$40.33	8.798%	$43.8782	$43.88	$43.90	$43.90
7 purchase totals =	$971.25		$1,053.4305	$1,053.43	$1,053.45	$1,053.30