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 $215.47   9.606%   $236.168   $236.17   $236.15   $236.20  
  Purchase #2 $208.99   8.788%   $227.356   $227.36   $227.35   $227.40  
  Purchase #3 $135.84   9.779%   $149.1238   $149.12   $149.10   $149.10  
  Purchase #4 $203.93   5.119%   $214.3692   $214.37   $214.35   $214.40  
  Purchase #5 $147.30   11.475%   $164.2027   $164.20   $164.20   $164.20  
  Purchase #6 $67.59   11.781%   $75.5528   $75.55   $75.55   $75.60  
  Purchase #7 $192.35   4.173%   $200.3768   $200.38   $200.40   $200.40  
  7 purchase totals = $1,171.47       $1,267.1493   $1,267.15   $1,267.10   $1,267.30