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 $195.99   6.250%   $208.2394   $208.24   $208.25   $208.20  
  Purchase #2 $129.72   4.844%   $136.0036   $136.00   $136.00   $136.00  
  Purchase #3 $54.76   3.857%   $56.8721   $56.87   $56.85   $56.90  
  Purchase #4 $135.67   8.271%   $146.8913   $146.89   $146.90   $146.90  
  Purchase #5 $111.41   13.783%   $126.7656   $126.77   $126.75   $126.80  
  Purchase #6 $241.57   13.205%   $273.4693   $273.47   $273.45   $273.50  
  Purchase #7 $171.74   3.809%   $178.2816   $178.28   $178.30   $178.30  
  7 purchase totals = $1,040.86       $1,126.5229   $1,126.52   $1,126.50   $1,126.60