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 $95.54   9.658%   $104.7673   $104.77   $104.75   $104.80  
  Purchase #2 $44.51   3.803%   $46.2027   $46.20   $46.20   $46.20  
  Purchase #3 $124.49   13.661%   $141.4966   $141.50   $141.50   $141.50  
  Purchase #4 $179.88   9.533%   $197.028   $197.03   $197.05   $197.00  
  Purchase #5 $61.34   3.586%   $63.5397   $63.54   $63.55   $63.50  
  Purchase #6 $46.77   12.357%   $52.5494   $52.55   $52.55   $52.50  
  Purchase #7 $150.79   7.457%   $162.0344   $162.03   $162.05   $162.00  
  7 purchase totals = $703.32       $767.6181   $767.62   $767.65   $767.50