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	$144.77	12.491%	$162.8532	$162.85	$162.85	$162.90
Purchase #2	$228.31	8.638%	$248.0314	$248.03	$248.05	$248.00
Purchase #3	$232.34	12.302%	$260.9225	$260.92	$260.90	$260.90
Purchase #4	$104.86	7.747%	$112.9835	$112.98	$113.00	$113.00
Purchase #5	$52.33	4.567%	$54.7199	$54.72	$54.70	$54.70
Purchase #6	$67.75	7.151%	$72.5948	$72.59	$72.60	$72.60
Purchase #7	$105.27	3.835%	$109.3071	$109.31	$109.30	$109.30
7 purchase totals =	$935.63		$1,021.4124	$1,021.40	$1,021.40	$1,021.40