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 $56.61   11.212%   $62.9571   $62.96   $62.95   $63.00  
  Purchase #2 $14.65   8.870%   $15.9495   $15.95   $15.95   $15.90  
  Purchase #3 $242.84   6.109%   $257.6751   $257.68   $257.70   $257.70  
  Purchase #4 $197.52   3.124%   $203.6905   $203.69   $203.70   $203.70  
  Purchase #5 $214.55   9.490%   $234.9108   $234.91   $234.90   $234.90  
  Purchase #6 $242.78   8.797%   $264.1374   $264.14   $264.15   $264.10  
  Purchase #7 $34.73   7.629%   $37.3796   $37.38   $37.40   $37.40  
  7 purchase totals = $1,003.68       $1,076.7000   $1,076.71   $1,076.75   $1,076.70