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 $224.96   3.691%   $233.2633   $233.26   $233.25   $233.30  
  Purchase #2 $8.49   11.201%   $9.441   $9.44   $9.45   $9.40  
  Purchase #3 $247.66   5.417%   $261.0757   $261.08   $261.10   $261.10  
  Purchase #4 $16.75   12.567%   $18.855   $18.86   $18.85   $18.90  
  Purchase #5 $223.35   3.143%   $230.3699   $230.37   $230.35   $230.40  
  Purchase #6 $243.68   8.686%   $264.846   $264.85   $264.85   $264.80  
  Purchase #7 $85.91   7.822%   $92.6299   $92.63   $92.65   $92.60  
  7 purchase totals = $1,050.80       $1,110.4808   $1,110.49   $1,110.50   $1,110.50