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	$40.84	9.342%	$44.6553	$44.66	$44.65	$44.70
Purchase #2	$32.47	3.267%	$33.5308	$33.53	$33.55	$33.50
Purchase #3	$174.25	6.140%	$184.949	$184.95	$184.95	$184.90
Purchase #4	$105.29	13.548%	$119.5547	$119.55	$119.55	$119.60
Purchase #5	$87.69	3.688%	$90.924	$90.92	$90.90	$90.90
Purchase #6	$100.35	3.630%	$103.9927	$103.99	$104.00	$104.00
Purchase #7	$223.37	6.452%	$237.7818	$237.78	$237.80	$237.80
7 purchase totals =	$764.26		$815.3883	$815.38	$815.40	$815.40