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 $196.63   7.172%   $210.7323   $210.73   $210.75   $210.70  
  Purchase #2 $172.41   11.167%   $191.663   $191.66   $191.65   $191.70  
  Purchase #3 $173.38   3.607%   $179.6338   $179.63   $179.65   $179.60  
  Purchase #4 $13.59   12.737%   $15.321   $15.32   $15.30   $15.30  
  Purchase #5 $116.47   8.817%   $126.7392   $126.74   $126.75   $126.70  
  Purchase #6 $168.63   6.702%   $179.9316   $179.93   $179.95   $179.90  
  Purchase #7 $208.27   11.188%   $231.5712   $231.57   $231.55   $231.60  
  7 purchase totals = $1,049.38       $1,135.5921   $1,135.58   $1,135.60   $1,135.50