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 $56.30   11.800%   $62.9434   $62.94   $62.95   $62.90  
  Purchase #2 $197.81   3.488%   $204.7096   $204.71   $204.70   $204.70  
  Purchase #3 $222.98   8.156%   $241.1662   $241.17   $241.15   $241.20  
  Purchase #4 $238.64   8.200%   $258.2085   $258.21   $258.20   $258.20  
  Purchase #5 $172.61   6.415%   $183.6829   $183.68   $183.70   $183.70  
  Purchase #6 $217.98   10.301%   $240.4341   $240.43   $240.45   $240.40  
  Purchase #7 $26.27   9.537%   $28.7754   $28.78   $28.80   $28.80  
  7 purchase totals = $1,132.59       $1,219.9201   $1,219.92   $1,219.95   $1,219.90