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 $33.81   3.312%   $34.9298   $34.93   $34.95   $34.90  
  Purchase #2 $168.71   5.298%   $177.6483   $177.65   $177.65   $177.60  
  Purchase #3 $86.43   11.301%   $96.1975   $96.20   $96.20   $96.20  
  Purchase #4 $99.44   9.668%   $109.0539   $109.05   $109.05   $109.10  
  Purchase #5 $209.69   9.617%   $229.8559   $229.86   $229.85   $229.90  
  Purchase #6 $188.47   6.767%   $201.2238   $201.22   $201.20   $201.20  
  Purchase #7 $104.65   13.350%   $118.6208   $118.62   $118.60   $118.60  
  7 purchase totals = $891.20       $967.5300   $967.53   $967.50   $967.50