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 $38.71   12.410%   $43.5139   $43.51   $43.50   $43.50  
  Purchase #2 $95.60   10.203%   $105.3541   $105.35   $105.35   $105.40  
  Purchase #3 $211.77   10.513%   $234.0334   $234.03   $234.05   $234.00  
  Purchase #4 $96.27   8.391%   $104.348   $104.35   $104.35   $104.30  
  Purchase #5 $117.62   11.824%   $131.5274   $131.53   $131.55   $131.50  
  Purchase #6 $177.49   8.248%   $192.1294   $192.13   $192.15   $192.10  
  Purchase #7 $211.25   12.651%   $237.9752   $237.98   $238.00   $238.00  
  7 purchase totals = $948.71       $1,048.8814   $1,048.88   $1,048.95   $1,048.80