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	$237.63	6.745%	$253.6581	$253.66	$253.65	$253.70
Purchase #2	$242.54	8.239%	$262.5229	$262.52	$262.50	$262.50
Purchase #3	$153.44	4.243%	$159.9505	$159.95	$159.95	$160.00
Purchase #4	$135.34	3.426%	$139.9767	$139.98	$140.00	$140.00
Purchase #5	$94.86	11.223%	$105.5061	$105.51	$105.50	$105.50
Purchase #6	$227.78	12.801%	$256.9381	$256.94	$256.95	$256.90
Purchase #7	$82.93	4.200%	$86.4131	$86.41	$86.40	$86.40
7 purchase totals =	$1,174.52		$1,264.9655	$1,264.97	$1,264.95	$1,265.00