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 $181.75   11.662%   $202.9457   $202.95   $202.95   $202.90  
  Purchase #2 $130.93   10.705%   $144.9461   $144.95   $144.95   $144.90  
  Purchase #3 $65.51   12.733%   $73.8514   $73.85   $73.85   $73.90  
  Purchase #4 $123.94   11.503%   $138.1968   $138.20   $138.20   $138.20  
  Purchase #5 $211.99   12.684%   $238.8788   $238.88   $238.90   $238.90  
  Purchase #6 $66.44   13.176%   $75.1941   $75.19   $75.20   $75.20  
  Purchase #7 $220.57   9.798%   $242.1814   $242.18   $242.20   $242.20  
  7 purchase totals = $1,001.13       $1,116.1943   $1,116.20   $1,116.25   $1,116.20