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 $191.88   5.271%   $201.994   $201.99   $202.00   $202.00  
  Purchase #2 $168.35   11.738%   $188.1109   $188.11   $188.10   $188.10  
  Purchase #3 $82.33   12.774%   $92.8468   $92.85   $92.85   $92.80  
  Purchase #4 $233.89   9.501%   $256.1119   $256.11   $256.10   $256.10  
  Purchase #5 $124.26   10.102%   $136.8127   $136.81   $136.80   $136.80  
  Purchase #6 $93.96   11.549%   $104.8114   $104.81   $104.80   $104.80  
  Purchase #7 $238.69   12.339%   $268.142   $268.14   $268.15   $268.10  
  7 purchase totals = $1,133.36       $1,248.8297   $1,248.82   $1,248.80   $1,248.70