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	$186.45	12.504%	$209.7637	$209.76	$209.75	$209.80
Purchase #2	$83.56	3.808%	$86.742	$86.74	$86.75	$86.70
Purchase #3	$60.57	3.143%	$62.4737	$62.47	$62.45	$62.50
Purchase #4	$249.97	11.452%	$278.5966	$278.60	$278.60	$278.60
Purchase #5	$181.50	9.602%	$198.9276	$198.93	$198.95	$198.90
Purchase #6	$31.39	3.524%	$32.4962	$32.50	$32.50	$32.50
Purchase #7	$161.39	4.582%	$168.7849	$168.78	$168.80	$168.80
7 purchase totals =	$954.83		$1,037.7847	$1,037.78	$1,037.80	$1,037.80