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	$35.30	4.709%	$36.9623	$36.96	$36.95	$37.00
Purchase #2	$84.51	7.197%	$90.5922	$90.59	$90.60	$90.60
Purchase #3	$117.60	11.161%	$130.7253	$130.73	$130.75	$130.70
Purchase #4	$215.59	12.704%	$242.9786	$242.98	$243.00	$243.00
Purchase #5	$113.37	12.361%	$127.3837	$127.38	$127.40	$127.40
Purchase #6	$21.35	4.870%	$22.3897	$22.39	$22.40	$22.40
Purchase #7	$154.91	5.500%	$163.4301	$163.43	$163.45	$163.40
7 purchase totals =	$742.63		$814.4619	$814.46	$814.55	$814.50