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	$249.56	3.672%	$258.7238	$258.72	$258.70	$258.70
Purchase #2	$49.49	8.179%	$53.5378	$53.54	$53.55	$53.50
Purchase #3	$244.87	11.365%	$272.6995	$272.70	$272.70	$272.70
Purchase #4	$102.48	6.819%	$109.4681	$109.47	$109.45	$109.50
Purchase #5	$206.69	6.204%	$219.513	$219.51	$219.50	$219.50
Purchase #6	$13.39	11.747%	$14.9629	$14.96	$14.95	$15.00
Purchase #7	$76.82	7.606%	$82.6629	$82.66	$82.65	$82.70
7 purchase totals =	$943.30		$1,011.5680	$1,011.56	$1,011.50	$1,011.60