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 $177.38   9.140%   $193.5925   $193.59   $193.60   $193.60  
  Purchase #2 $49.37   8.740%   $53.6849   $53.68   $53.70   $53.70  
  Purchase #3 $41.71   10.358%   $46.0303   $46.03   $46.05   $46.00  
  Purchase #4 $13.30   9.243%   $14.5293   $14.53   $14.55   $14.50  
  Purchase #5 $242.93   10.665%   $268.8385   $268.84   $268.85   $268.80  
  Purchase #6 $187.81   11.641%   $209.673   $209.67   $209.65   $209.70  
  Purchase #7 $100.32   10.302%   $110.655   $110.66   $110.65   $110.70  
  7 purchase totals = $812.82       $897.0035   $897.00   $897.05   $897.00