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 $181.54   8.478%   $196.931   $196.93   $196.95   $196.90  
  Purchase #2 $241.76   7.366%   $259.568   $259.57   $259.55   $259.60  
  Purchase #3 $230.25   7.744%   $248.0806   $248.08   $248.10   $248.10  
  Purchase #4 $31.46   11.209%   $34.9864   $34.99   $35.00   $35.00  
  Purchase #5 $165.46   8.598%   $179.6863   $179.69   $179.70   $179.70  
  Purchase #6 $243.74   8.703%   $264.9527   $264.95   $264.95   $265.00  
  Purchase #7 $244.81   5.122%   $257.3492   $257.35   $257.35   $257.30  
  7 purchase totals = $1,339.02       $1,441.5542   $1,441.56   $1,441.60   $1,441.60