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 $68.50   7.513%   $73.6464   $73.65   $73.65   $73.60  
  Purchase #2 $104.56   12.404%   $117.5296   $117.53   $117.55   $117.50  
  Purchase #3 $208.46   10.792%   $230.957   $230.96   $230.95   $231.00  
  Purchase #4 $207.46   5.429%   $218.723   $218.72   $218.70   $218.70  
  Purchase #5 $246.29   10.742%   $272.7465   $272.75   $272.75   $272.70  
  Purchase #6 $28.92   5.408%   $30.484   $30.48   $30.50   $30.50  
  Purchase #7 $102.79   4.588%   $107.506   $107.51   $107.50   $107.50  
  7 purchase totals = $966.98       $1,051.5925   $1,051.60   $1,051.60   $1,051.50