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 $59.92   3.533%   $62.037   $62.04   $62.05   $62.00  
  Purchase #2 $230.79   4.393%   $240.9286   $240.93   $240.95   $240.90  
  Purchase #3 $105.79   3.568%   $109.5646   $109.56   $109.55   $109.60  
  Purchase #4 $36.77   12.152%   $41.2383   $41.24   $41.25   $41.20  
  Purchase #5 $179.88   10.556%   $198.8681   $198.87   $198.85   $198.90  
  Purchase #6 $18.81   12.611%   $21.1821   $21.18   $21.20   $21.20  
  Purchase #7 $184.37   9.254%   $201.4316   $201.43   $201.45   $201.40  
  7 purchase totals = $816.33       $875.2503   $875.25   $875.30   $875.20