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 $101.65   11.357%   $113.1944   $113.19   $113.20   $113.20  
  Purchase #2 $125.48   9.621%   $137.5524   $137.55   $137.55   $137.60  
  Purchase #3 $116.87   7.826%   $126.0162   $126.02   $126.00   $126.00  
  Purchase #4 $162.33   3.263%   $167.6268   $167.63   $167.65   $167.60  
  Purchase #5 $121.56   8.661%   $132.0883   $132.09   $132.10   $132.10  
  Purchase #6 $174.90   10.746%   $193.6948   $193.69   $193.70   $193.70  
  Purchase #7 $169.64   5.689%   $179.2908   $179.29   $179.30   $179.30  
  7 purchase totals = $972.43       $1,049.4637   $1,049.46   $1,049.50   $1,049.50