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	$112.89	10.387%	$124.6159	$124.62	$124.60	$124.60
Purchase #2	$10.67	5.761%	$11.2847	$11.28	$11.30	$11.30
Purchase #3	$199.73	5.271%	$210.2578	$210.26	$210.25	$210.30
Purchase #4	$99.26	4.712%	$103.9371	$103.94	$103.95	$103.90
Purchase #5	$201.95	3.185%	$208.3821	$208.38	$208.40	$208.40
Purchase #6	$213.48	3.270%	$220.4608	$220.46	$220.45	$220.50
Purchase #7	$139.50	9.588%	$152.8753	$152.88	$152.90	$152.90
7 purchase totals =	$977.48		$1,031.8137	$1,031.82	$1,031.85	$1,031.90