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 $82.58   11.324%   $91.9314   $91.93   $91.95   $91.90  
  Purchase #2 $236.75   4.452%   $247.2901   $247.29   $247.30   $247.30  
  Purchase #3 $30.56   10.278%   $33.701   $33.70   $33.70   $33.70  
  Purchase #4 $113.31   5.636%   $119.6962   $119.70   $119.70   $119.70  
  Purchase #5 $224.67   9.336%   $245.6452   $245.65   $245.65   $245.60  
  Purchase #6 $161.57   12.676%   $182.0506   $182.05   $182.05   $182.10  
  Purchase #7 $203.66   5.758%   $215.3867   $215.39   $215.40   $215.40  
  7 purchase totals = $1,053.10       $1,135.7012   $1,135.71   $1,135.75   $1,135.70