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	$113.76	12.249%	$127.6945	$127.69	$127.70	$127.70
Purchase #2	$126.72	10.755%	$140.3487	$140.35	$140.35	$140.30
Purchase #3	$64.58	11.827%	$72.2179	$72.22	$72.20	$72.20
Purchase #4	$176.72	7.800%	$190.5042	$190.50	$190.50	$190.50
Purchase #5	$177.91	9.565%	$194.9271	$194.93	$194.95	$194.90
Purchase #6	$231.39	6.172%	$245.6714	$245.67	$245.65	$245.70
Purchase #7	$118.59	12.333%	$133.2157	$133.22	$133.20	$133.20
7 purchase totals =	$1,009.67		$1,104.5795	$1,104.58	$1,104.55	$1,104.50