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 $201.50   6.602%   $214.803   $214.80   $214.80   $214.80  
  Purchase #2 $86.37   12.385%   $97.0669   $97.07   $97.05   $97.10  
  Purchase #3 $109.91   8.613%   $119.3765   $119.38   $119.40   $119.40  
  Purchase #4 $237.78   12.788%   $268.1873   $268.19   $268.20   $268.20  
  Purchase #5 $22.66   8.702%   $24.6319   $24.63   $24.65   $24.60  
  Purchase #6 $90.53   11.201%   $100.6703   $100.67   $100.65   $100.70  
  Purchase #7 $184.51   9.553%   $202.1362   $202.14   $202.15   $202.10  
  7 purchase totals = $933.26       $1,026.8721   $1,026.88   $1,026.90   $1,026.90