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	$231.52	13.566%	$262.928	$262.93	$262.95	$262.90
Purchase #2	$100.25	8.422%	$108.6931	$108.69	$108.70	$108.70
Purchase #3	$238.67	10.565%	$263.8855	$263.89	$263.90	$263.90
Purchase #4	$160.56	13.751%	$182.6386	$182.64	$182.65	$182.60
Purchase #5	$38.96	3.593%	$40.3598	$40.36	$40.35	$40.40
Purchase #6	$125.34	4.599%	$131.1044	$131.10	$131.10	$131.10
Purchase #7	$82.53	5.533%	$87.0964	$87.10	$87.10	$87.10
7 purchase totals =	$977.83		$1,076.7058	$1,076.71	$1,076.75	$1,076.70