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	$196.97	9.618%	$215.9146	$215.91	$215.90	$215.90
Purchase #2	$123.40	13.742%	$140.3576	$140.36	$140.35	$140.40
Purchase #3	$105.81	12.113%	$118.6268	$118.63	$118.65	$118.60
Purchase #4	$241.89	5.644%	$255.5423	$255.54	$255.55	$255.50
Purchase #5	$88.29	7.126%	$94.5815	$94.58	$94.60	$94.60
Purchase #6	$76.95	4.730%	$80.5897	$80.59	$80.60	$80.60
Purchase #7	$88.97	3.709%	$92.2699	$92.27	$92.25	$92.30
7 purchase totals =	$922.28		$997.8824	$997.88	$997.90	$997.90