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 $214.50   10.449%   $236.9131   $236.91   $236.90   $236.90  
  Purchase #2 $191.64   10.467%   $211.699   $211.70   $211.70   $211.70  
  Purchase #3 $95.43   7.447%   $102.5367   $102.54   $102.55   $102.50  
  Purchase #4 $48.90   7.637%   $52.6345   $52.63   $52.65   $52.60  
  Purchase #5 $246.77   8.188%   $266.9755   $266.98   $267.00   $267.00  
  Purchase #6 $87.70   12.380%   $98.5573   $98.56   $98.55   $98.60  
  Purchase #7 $69.87   8.151%   $75.5651   $75.57   $75.55   $75.60  
  7 purchase totals = $954.81       $1,044.8812   $1,044.89   $1,044.90   $1,044.90