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	$124.63	5.525%	$131.5158	$131.52	$131.50	$131.50
Purchase #2	$75.49	4.102%	$78.5866	$78.59	$78.60	$78.60
Purchase #3	$27.49	4.329%	$28.68	$28.68	$28.70	$28.70
Purchase #4	$224.84	7.867%	$242.5282	$242.53	$242.55	$242.50
Purchase #5	$84.80	7.113%	$90.8318	$90.83	$90.85	$90.80
Purchase #6	$79.54	10.557%	$87.937	$87.94	$87.95	$87.90
Purchase #7	$78.63	7.302%	$84.3716	$84.37	$84.35	$84.40
7 purchase totals =	$695.42		$744.4510	$744.46	$744.50	$744.40