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	$154.39	8.514%	$167.5348	$167.53	$167.55	$167.50
Purchase #2	$123.34	5.727%	$130.4037	$130.40	$130.40	$130.40
Purchase #3	$179.79	7.329%	$192.9668	$192.97	$192.95	$193.00
Purchase #4	$100.55	3.365%	$103.9335	$103.93	$103.95	$103.90
Purchase #5	$143.70	8.131%	$155.3842	$155.38	$155.40	$155.40
Purchase #6	$127.57	11.508%	$142.2508	$142.25	$142.25	$142.30
Purchase #7	$141.55	7.311%	$151.8987	$151.90	$151.90	$151.90
7 purchase totals =	$970.89		$1,044.3725	$1,044.36	$1,044.40	$1,044.40