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 $24.26   5.510%   $25.5967   $25.60   $25.60   $25.60  
  Purchase #2 $214.95   8.218%   $232.6146   $232.61   $232.60   $232.60  
  Purchase #3 $196.94   3.539%   $203.9097   $203.91   $203.90   $203.90  
  Purchase #4 $237.79   8.320%   $257.5741   $257.57   $257.55   $257.60  
  Purchase #5 $219.41   8.212%   $237.4279   $237.43   $237.45   $237.40  
  Purchase #6 $94.71   8.791%   $103.036   $103.04   $103.05   $103.00  
  Purchase #7 $26.43   4.777%   $27.6926   $27.69   $27.70   $27.70  
  7 purchase totals = $1,014.49       $1,087.8516   $1,087.85   $1,087.85   $1,087.80