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	$80.90	7.423%	$86.9052	$86.91	$86.90	$86.90
Purchase #2	$207.85	9.378%	$227.3422	$227.34	$227.35	$227.30
Purchase #3	$107.40	11.357%	$119.5974	$119.60	$119.60	$119.60
Purchase #4	$179.66	3.709%	$186.3236	$186.32	$186.30	$186.30
Purchase #5	$148.82	11.262%	$165.5801	$165.58	$165.60	$165.60
Purchase #6	$90.97	13.366%	$103.1291	$103.13	$103.15	$103.10
Purchase #7	$244.48	4.603%	$255.7334	$255.73	$255.75	$255.70
7 purchase totals =	$1,060.08		$1,144.6110	$1,144.61	$1,144.65	$1,144.50