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	$217.94	12.137%	$244.3914	$244.39	$244.40	$244.40
Purchase #2	$6.91	5.253%	$7.273	$7.27	$7.25	$7.30
Purchase #3	$145.86	12.227%	$163.6943	$163.69	$163.70	$163.70
Purchase #4	$73.72	12.517%	$82.9475	$82.95	$82.95	$82.90
Purchase #5	$7.39	13.156%	$8.3622	$8.36	$8.35	$8.40
Purchase #6	$12.45	3.522%	$12.8885	$12.89	$12.90	$12.90
Purchase #7	$142.56	3.383%	$147.3828	$147.38	$147.40	$147.40
7 purchase totals =	$606.83		$666.9397	$666.93	$666.95	$667.00