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 $105.25   10.406%   $116.2023   $116.20   $116.20   $116.20  
  Purchase #2 $23.25   12.578%   $26.1744   $26.17   $26.15   $26.20  
  Purchase #3 $116.43   9.588%   $127.5933   $127.59   $127.60   $127.60  
  Purchase #4 $234.94   13.247%   $266.0625   $266.06   $266.05   $266.10  
  Purchase #5 $199.63   12.524%   $224.6317   $224.63   $224.65   $224.60  
  Purchase #6 $164.99   5.471%   $174.0166   $174.02   $174.00   $174.00  
  Purchase #7 $87.26   12.157%   $97.8682   $97.87   $97.85   $97.90  
  7 purchase totals = $931.75       $1,032.5490   $1,032.54   $1,032.50   $1,032.60