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	$140.51	9.582%	$153.9737	$153.97	$153.95	$154.00
Purchase #2	$196.30	13.289%	$222.3863	$222.39	$222.40	$222.40
Purchase #3	$104.35	8.180%	$112.8858	$112.89	$112.90	$112.90
Purchase #4	$91.78	3.681%	$95.1584	$95.16	$95.15	$95.20
Purchase #5	$37.31	4.237%	$38.8908	$38.89	$38.90	$38.90
Purchase #6	$136.40	13.828%	$155.2614	$155.26	$155.25	$155.30
Purchase #7	$81.63	11.237%	$90.8028	$90.80	$90.80	$90.80
7 purchase totals =	$788.28		$869.3592	$869.36	$869.35	$869.50