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	$67.47	7.244%	$72.3575	$72.36	$72.35	$72.40
Purchase #2	$197.99	8.717%	$215.2488	$215.25	$215.25	$215.20
Purchase #3	$189.71	13.376%	$215.0856	$215.09	$215.10	$215.10
Purchase #4	$103.73	8.184%	$112.2193	$112.22	$112.20	$112.20
Purchase #5	$167.60	10.311%	$184.8812	$184.88	$184.90	$184.90
Purchase #6	$233.84	5.238%	$246.0885	$246.09	$246.10	$246.10
Purchase #7	$18.58	12.197%	$20.8462	$20.85	$20.85	$20.80
7 purchase totals =	$978.92		$1,066.7271	$1,066.74	$1,066.75	$1,066.70