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	$104.47	11.648%	$116.6387	$116.64	$116.65	$116.60
Purchase #2	$154.53	10.591%	$170.8963	$170.90	$170.90	$170.90
Purchase #3	$75.98	3.387%	$78.5534	$78.55	$78.55	$78.60
Purchase #4	$127.58	13.231%	$144.4601	$144.46	$144.45	$144.50
Purchase #5	$239.59	9.673%	$262.7655	$262.77	$262.75	$262.80
Purchase #6	$64.35	9.524%	$70.4787	$70.48	$70.50	$70.50
Purchase #7	$158.68	7.833%	$171.1094	$171.11	$171.10	$171.10
7 purchase totals =	$925.18		$1,014.9021	$1,014.91	$1,014.90	$1,015.00