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	$6.62	4.280%	$6.9033	$6.90	$6.90	$6.90
Purchase #2	$177.42	10.480%	$196.0136	$196.01	$196.00	$196.00
Purchase #3	$132.88	13.534%	$150.864	$150.86	$150.85	$150.90
Purchase #4	$226.82	3.364%	$234.4502	$234.45	$234.45	$234.50
Purchase #5	$107.48	6.315%	$114.2674	$114.27	$114.25	$114.30
Purchase #6	$208.30	6.725%	$222.3082	$222.31	$222.30	$222.30
Purchase #7	$177.83	4.347%	$185.5603	$185.56	$185.55	$185.60
7 purchase totals =	$1,037.35		$1,110.3670	$1,110.36	$1,110.30	$1,110.50