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	$65.31	9.368%	$71.4282	$71.43	$71.45	$71.40
Purchase #2	$29.50	13.549%	$33.497	$33.50	$33.50	$33.50
Purchase #3	$171.85	10.530%	$189.9458	$189.95	$189.95	$189.90
Purchase #4	$136.74	6.245%	$145.2794	$145.28	$145.30	$145.30
Purchase #5	$247.84	6.673%	$264.3784	$264.38	$264.40	$264.40
Purchase #6	$140.31	7.265%	$150.5035	$150.50	$150.50	$150.50
Purchase #7	$164.90	9.709%	$180.9101	$180.91	$180.90	$180.90
7 purchase totals =	$956.45		$1,035.9424	$1,035.95	$1,036.00	$1,035.90