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 $111.32   13.144%   $125.9519   $125.95   $125.95   $126.00  
  Purchase #2 $124.44   9.834%   $136.6774   $136.68   $136.70   $136.70  
  Purchase #3 $204.53   7.683%   $220.244   $220.24   $220.25   $220.20  
  Purchase #4 $181.99   8.505%   $197.4682   $197.47   $197.45   $197.50  
  Purchase #5 $146.36   12.357%   $164.4457   $164.45   $164.45   $164.40  
  Purchase #6 $58.94   10.861%   $65.3415   $65.34   $65.35   $65.30  
  Purchase #7 $154.32   6.843%   $164.8801   $164.88   $164.90   $164.90  
  7 purchase totals = $981.90       $1,075.0088   $1,075.01   $1,075.05   $1,075.00