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 $82.69   6.199%   $87.816   $87.82   $87.80   $87.80  
  Purchase #2 $246.41   6.319%   $261.9806   $261.98   $262.00   $262.00  
  Purchase #3 $68.57   13.514%   $77.8365   $77.84   $77.85   $77.80  
  Purchase #4 $217.66   9.155%   $237.5868   $237.59   $237.60   $237.60  
  Purchase #5 $249.74   6.503%   $265.9806   $265.98   $266.00   $266.00  
  Purchase #6 $165.34   5.624%   $174.6387   $174.64   $174.65   $174.60  
  Purchase #7 $90.98   5.681%   $96.1486   $96.15   $96.15   $96.10  
  7 purchase totals = $1,121.39       $1,201.9878   $1,202.00   $1,202.05   $1,201.90