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	$236.72	13.761%	$269.295	$269.30	$269.30	$269.30
Purchase #2	$217.35	13.269%	$246.1902	$246.19	$246.20	$246.20
Purchase #3	$41.46	5.788%	$43.8597	$43.86	$43.85	$43.90
Purchase #4	$195.54	12.231%	$219.4565	$219.46	$219.45	$219.50
Purchase #5	$150.62	13.595%	$171.0968	$171.10	$171.10	$171.10
Purchase #6	$55.33	13.664%	$62.8903	$62.89	$62.90	$62.90
Purchase #7	$76.40	4.745%	$80.0252	$80.03	$80.05	$80.00
7 purchase totals =	$973.42		$1,092.8137	$1,092.83	$1,092.85	$1,092.90