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	$53.46	7.310%	$57.3679	$57.37	$57.35	$57.40
Purchase #2	$102.94	8.280%	$111.4634	$111.46	$111.45	$111.50
Purchase #3	$46.62	11.336%	$51.9048	$51.90	$51.90	$51.90
Purchase #4	$75.45	10.434%	$83.3225	$83.32	$83.30	$83.30
Purchase #5	$217.90	12.534%	$245.2116	$245.21	$245.20	$245.20
Purchase #6	$103.44	9.245%	$113.003	$113.00	$113.00	$113.00
Purchase #7	$67.99	7.870%	$73.3408	$73.34	$73.35	$73.30
7 purchase totals =	$667.80		$735.6140	$735.60	$735.55	$735.60