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	$31.66	3.220%	$32.6795	$32.68	$32.70	$32.70
Purchase #2	$84.68	12.318%	$95.1109	$95.11	$95.10	$95.10
Purchase #3	$217.78	9.691%	$238.8851	$238.89	$238.90	$238.90
Purchase #4	$52.95	3.217%	$54.6534	$54.65	$54.65	$54.70
Purchase #5	$115.72	3.390%	$119.6429	$119.64	$119.65	$119.60
Purchase #6	$132.86	11.757%	$148.4804	$148.48	$148.50	$148.50
Purchase #7	$16.39	12.409%	$18.4238	$18.42	$18.40	$18.40
7 purchase totals =	$652.04		$707.8760	$707.87	$707.90	$707.90