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 $214.60   4.495%   $224.2463   $224.25   $224.25   $224.20  
  Purchase #2 $247.63   12.232%   $277.9201   $277.92   $277.90   $277.90  
  Purchase #3 $199.77   4.337%   $208.434   $208.43   $208.45   $208.40  
  Purchase #4 $96.91   8.708%   $105.3489   $105.35   $105.35   $105.30  
  Purchase #5 $228.75   11.461%   $254.967   $254.97   $254.95   $255.00  
  Purchase #6 $130.26   9.582%   $142.7415   $142.74   $142.75   $142.70  
  Purchase #7 $92.43   8.348%   $100.1461   $100.15   $100.15   $100.10  
  7 purchase totals = $1,210.35       $1,313.8039   $1,313.81   $1,313.80   $1,313.60