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 $49.36   6.757%   $52.6953   $52.70   $52.70   $52.70  
  Purchase #2 $147.69   4.311%   $154.0569   $154.06   $154.05   $154.10  
  Purchase #3 $11.38   10.382%   $12.5615   $12.56   $12.55   $12.60  
  Purchase #4 $178.78   5.554%   $188.7094   $188.71   $188.70   $188.70  
  Purchase #5 $201.51   6.663%   $214.9366   $214.94   $214.95   $214.90  
  Purchase #6 $65.59   13.157%   $74.2197   $74.22   $74.20   $74.20  
  Purchase #7 $198.74   8.151%   $214.9393   $214.94   $214.95   $214.90  
  7 purchase totals = $853.05       $912.1187   $912.13   $912.10   $912.10