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	$147.60	6.334%	$156.949	$156.95	$156.95	$156.90
Purchase #2	$229.86	13.354%	$260.5555	$260.56	$260.55	$260.60
Purchase #3	$167.80	8.377%	$181.8566	$181.86	$181.85	$181.90
Purchase #4	$148.79	13.533%	$168.9258	$168.93	$168.95	$168.90
Purchase #5	$228.34	4.367%	$238.3116	$238.31	$238.30	$238.30
Purchase #6	$39.99	10.257%	$44.0918	$44.09	$44.10	$44.10
Purchase #7	$92.33	9.230%	$100.8521	$100.85	$100.85	$100.90
7 purchase totals =	$1,054.71		$1,151.5424	$1,151.55	$1,151.55	$1,151.60