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 $38.81   13.318%   $43.9787   $43.98   $44.00   $44.00  
  Purchase #2 $206.55   12.335%   $232.0279   $232.03   $232.05   $232.00  
  Purchase #3 $179.51   13.736%   $204.1675   $204.17   $204.15   $204.20  
  Purchase #4 $104.95   13.561%   $119.1823   $119.18   $119.20   $119.20  
  Purchase #5 $57.70   4.649%   $60.3825   $60.38   $60.40   $60.40  
  Purchase #6 $225.66   4.738%   $236.3518   $236.35   $236.35   $236.40  
  Purchase #7 $32.47   11.545%   $36.2187   $36.22   $36.20   $36.20  
  7 purchase totals = $845.65       $932.3094   $932.31   $932.35   $932.40