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	$123.60	11.381%	$137.6669	$137.67	$137.65	$137.70
Purchase #2	$171.48	11.340%	$190.9258	$190.93	$190.95	$190.90
Purchase #3	$153.36	4.150%	$159.7244	$159.72	$159.70	$159.70
Purchase #4	$186.39	5.577%	$196.785	$196.79	$196.80	$196.80
Purchase #5	$243.62	3.226%	$251.4792	$251.48	$251.50	$251.50
Purchase #6	$193.32	8.782%	$210.2974	$210.30	$210.30	$210.30
Purchase #7	$136.76	13.362%	$155.0339	$155.03	$155.05	$155.00
7 purchase totals =	$1,208.53		$1,301.9126	$1,301.92	$1,301.95	$1,301.90