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 $182.49   10.390%   $201.4507   $201.45   $201.45   $201.50  
  Purchase #2 $92.58   9.358%   $101.2436   $101.24   $101.25   $101.20  
  Purchase #3 $149.56   12.542%   $168.3178   $168.32   $168.30   $168.30  
  Purchase #4 $207.67   7.758%   $223.781   $223.78   $223.80   $223.80  
  Purchase #5 $112.42   9.465%   $123.0606   $123.06   $123.05   $123.10  
  Purchase #6 $244.56   5.869%   $258.9132   $258.91   $258.90   $258.90  
  Purchase #7 $107.44   12.374%   $120.7346   $120.73   $120.75   $120.70  
  7 purchase totals = $1,096.72       $1,197.5015   $1,197.49   $1,197.50   $1,197.50