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 $68.81   6.714%   $73.4299   $73.43   $73.45   $73.40  
  Purchase #2 $168.50   9.418%   $184.3693   $184.37   $184.35   $184.40  
  Purchase #3 $226.48   9.387%   $247.7397   $247.74   $247.75   $247.70  
  Purchase #4 $43.53   8.427%   $47.1983   $47.20   $47.20   $47.20  
  Purchase #5 $207.49   12.567%   $233.5653   $233.57   $233.55   $233.60  
  Purchase #6 $235.42   3.450%   $243.542   $243.54   $243.55   $243.50  
  Purchase #7 $57.31   13.202%   $64.8761   $64.88   $64.90   $64.90  
  7 purchase totals = $1,007.54       $1,094.7206   $1,094.73   $1,094.75   $1,094.70