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	$146.88	6.794%	$156.859	$156.86	$156.85	$156.90
Purchase #2	$213.32	5.616%	$225.3001	$225.30	$225.30	$225.30
Purchase #3	$168.83	10.127%	$185.9274	$185.93	$185.95	$185.90
Purchase #4	$106.43	6.641%	$113.498	$113.50	$113.50	$113.50
Purchase #5	$226.67	8.204%	$245.266	$245.27	$245.25	$245.30
Purchase #6	$240.37	12.747%	$271.01	$271.01	$271.00	$271.00
Purchase #7	$147.35	7.269%	$158.0609	$158.06	$158.05	$158.10
7 purchase totals =	$1,249.85		$1,355.9214	$1,355.93	$1,355.90	$1,356.00