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	$29.76	7.554%	$32.0081	$32.01	$32.00	$32.00
Purchase #2	$38.66	5.428%	$40.7585	$40.76	$40.75	$40.80
Purchase #3	$109.37	7.635%	$117.7204	$117.72	$117.70	$117.70
Purchase #4	$234.40	12.854%	$264.5298	$264.53	$264.55	$264.50
Purchase #5	$167.60	10.615%	$185.3907	$185.39	$185.40	$185.40
Purchase #6	$243.99	10.583%	$269.8115	$269.81	$269.80	$269.80
Purchase #7	$171.29	9.293%	$187.208	$187.21	$187.20	$187.20
7 purchase totals =	$995.07		$1,097.4270	$1,097.43	$1,097.40	$1,097.40