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	$13.33	8.686%	$14.4878	$14.49	$14.50	$14.50
Purchase #2	$36.75	5.173%	$38.6511	$38.65	$38.65	$38.70
Purchase #3	$156.88	9.296%	$171.4636	$171.46	$171.45	$171.50
Purchase #4	$10.77	6.776%	$11.4998	$11.50	$11.50	$11.50
Purchase #5	$36.83	5.842%	$38.9816	$38.98	$39.00	$39.00
Purchase #6	$116.55	5.864%	$123.3845	$123.38	$123.40	$123.40
Purchase #7	$232.53	11.432%	$259.1128	$259.11	$259.10	$259.10
7 purchase totals =	$603.64		$657.5812	$657.57	$657.60	$657.70