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 $71.66   6.262%   $76.1473   $76.15   $76.15   $76.10  
  Purchase #2 $59.61   5.201%   $62.7103   $62.71   $62.70   $62.70  
  Purchase #3 $181.81   11.193%   $202.16   $202.16   $202.15   $202.20  
  Purchase #4 $58.68   6.672%   $62.5951   $62.60   $62.60   $62.60  
  Purchase #5 $203.40   11.679%   $227.1551   $227.16   $227.15   $227.20  
  Purchase #6 $207.83   12.254%   $233.2975   $233.30   $233.30   $233.30  
  Purchase #7 $212.46   12.316%   $238.6266   $238.63   $238.65   $238.60  
  7 purchase totals = $995.45       $1,102.6919   $1,102.71   $1,102.70   $1,102.70