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	$13.25	10.202%	$14.6018	$14.60	$14.60	$14.60
Purchase #2	$137.51	13.452%	$156.0078	$156.01	$156.00	$156.00
Purchase #3	$207.59	7.681%	$223.535	$223.54	$223.55	$223.50
Purchase #4	$214.31	12.169%	$240.3894	$240.39	$240.40	$240.40
Purchase #5	$140.63	5.158%	$147.8837	$147.88	$147.90	$147.90
Purchase #6	$132.40	13.232%	$149.9192	$149.92	$149.90	$149.90
Purchase #7	$136.77	8.859%	$148.8865	$148.89	$148.90	$148.90
7 purchase totals =	$982.46		$1,081.2234	$1,081.23	$1,081.25	$1,081.20