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	$132.74	7.246%	$142.3583	$142.36	$142.35	$142.40
Purchase #2	$41.31	5.138%	$43.4325	$43.43	$43.45	$43.40
Purchase #3	$174.67	13.514%	$198.2749	$198.27	$198.25	$198.30
Purchase #4	$106.58	11.721%	$119.0722	$119.07	$119.05	$119.10
Purchase #5	$189.55	4.546%	$198.1669	$198.17	$198.15	$198.20
Purchase #6	$136.89	11.382%	$152.4708	$152.47	$152.45	$152.50
Purchase #7	$239.69	11.347%	$266.8876	$266.89	$266.90	$266.90
7 purchase totals =	$1,021.43		$1,120.6632	$1,120.66	$1,120.60	$1,120.80