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	$108.85	3.769%	$112.9526	$112.95	$112.95	$113.00
Purchase #2	$139.35	6.698%	$148.6837	$148.68	$148.70	$148.70
Purchase #3	$86.64	4.268%	$90.3378	$90.34	$90.35	$90.30
Purchase #4	$19.75	4.394%	$20.6178	$20.62	$20.60	$20.60
Purchase #5	$141.56	10.831%	$156.8924	$156.89	$156.90	$156.90
Purchase #6	$194.42	13.706%	$221.0672	$221.07	$221.05	$221.10
Purchase #7	$66.72	7.705%	$71.8608	$71.86	$71.85	$71.90
7 purchase totals =	$757.29		$822.4123	$822.41	$822.40	$822.50