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 $59.41   5.634%   $62.7572   $62.76   $62.75   $62.80  
  Purchase #2 $39.88   5.867%   $42.2198   $42.22   $42.20   $42.20  
  Purchase #3 $202.39   7.830%   $218.2371   $218.24   $218.25   $218.20  
  Purchase #4 $248.71   7.204%   $266.6271   $266.63   $266.65   $266.60  
  Purchase #5 $52.52   3.700%   $54.4632   $54.46   $54.45   $54.50  
  Purchase #6 $180.99   12.571%   $203.7423   $203.74   $203.75   $203.70  
  Purchase #7 $183.61   6.582%   $195.6952   $195.70   $195.70   $195.70  
  7 purchase totals = $967.51       $1,043.7419   $1,043.75   $1,043.75   $1,043.70