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 $114.45   3.265%   $118.1868   $118.19   $118.20   $118.20  
  Purchase #2 $135.74   5.706%   $143.4853   $143.49   $143.50   $143.50  
  Purchase #3 $118.84   13.492%   $134.8739   $134.87   $134.85   $134.90  
  Purchase #4 $200.61   3.281%   $207.192   $207.19   $207.20   $207.20  
  Purchase #5 $43.39   5.479%   $45.7673   $45.77   $45.75   $45.80  
  Purchase #6 $218.87   6.610%   $233.3373   $233.34   $233.35   $233.30  
  Purchase #7 $126.83   10.577%   $140.2448   $140.24   $140.25   $140.20  
  7 purchase totals = $958.73       $1,023.0874   $1,023.09   $1,023.10   $1,023.10