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	$164.83	11.297%	$183.4508	$183.45	$183.45	$183.50
Purchase #2	$121.55	12.258%	$136.4496	$136.45	$136.45	$136.40
Purchase #3	$216.50	10.544%	$239.3278	$239.33	$239.35	$239.30
Purchase #4	$90.61	4.495%	$94.6829	$94.68	$94.70	$94.70
Purchase #5	$158.43	3.534%	$164.0289	$164.03	$164.05	$164.00
Purchase #6	$134.31	4.186%	$139.9322	$139.93	$139.95	$139.90
Purchase #7	$70.82	10.651%	$78.363	$78.36	$78.35	$78.40
7 purchase totals =	$957.05		$1,036.2352	$1,036.23	$1,036.30	$1,036.20