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 $55.60   13.202%   $62.9403   $62.94   $62.95   $62.90  
  Purchase #2 $11.32   4.708%   $11.8529   $11.85   $11.85   $11.90  
  Purchase #3 $212.26   9.684%   $232.8153   $232.82   $232.80   $232.80  
  Purchase #4 $186.93   6.317%   $198.7384   $198.74   $198.75   $198.70  
  Purchase #5 $240.49   7.379%   $258.2358   $258.24   $258.25   $258.20  
  Purchase #6 $11.38   7.479%   $12.2311   $12.23   $12.25   $12.20  
  Purchase #7 $165.39   7.742%   $178.1945   $178.19   $178.20   $178.20  
  7 purchase totals = $883.37       $955.0083   $955.01   $955.05   $954.90