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	$24.25	7.145%	$25.9827	$25.98	$26.00	$26.00
Purchase #2	$190.80	11.291%	$212.3432	$212.34	$212.35	$212.30
Purchase #3	$246.54	3.665%	$255.5757	$255.58	$255.60	$255.60
Purchase #4	$243.71	7.595%	$262.2198	$262.22	$262.20	$262.20
Purchase #5	$37.30	8.358%	$40.4175	$40.42	$40.40	$40.40
Purchase #6	$153.96	6.752%	$164.3554	$164.36	$164.35	$164.40
Purchase #7	$49.94	8.821%	$54.3452	$54.35	$54.35	$54.30
7 purchase totals =	$946.50		$1,015.2395	$1,015.25	$1,015.25	$1,015.20