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	$233.82	6.262%	$248.4618	$248.46	$248.45	$248.50
Purchase #2	$105.59	7.295%	$113.2928	$113.29	$113.30	$113.30
Purchase #3	$150.91	3.265%	$155.8372	$155.84	$155.85	$155.80
Purchase #4	$11.53	12.377%	$12.9571	$12.96	$12.95	$13.00
Purchase #5	$207.35	5.683%	$219.1337	$219.13	$219.15	$219.10
Purchase #6	$188.25	4.198%	$196.1527	$196.15	$196.15	$196.20
Purchase #7	$89.44	6.710%	$95.4414	$95.44	$95.45	$95.40
7 purchase totals =	$986.89		$1,041.2767	$1,041.27	$1,041.30	$1,041.30