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 $194.66   11.861%   $217.7486   $217.75   $217.75   $217.70  
  Purchase #2 $208.73   12.358%   $234.5249   $234.52   $234.50   $234.50  
  Purchase #3 $30.49   13.157%   $34.5016   $34.50   $34.50   $34.50  
  Purchase #4 $211.48   8.136%   $228.686   $228.69   $228.70   $228.70  
  Purchase #5 $148.45   9.639%   $162.7591   $162.76   $162.75   $162.80  
  Purchase #6 $33.65   6.140%   $35.7161   $35.72   $35.70   $35.70  
  Purchase #7 $237.95   7.246%   $255.1919   $255.19   $255.20   $255.20  
  7 purchase totals = $1,065.41       $1,169.1282   $1,169.13   $1,169.10   $1,169.10