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 $107.47   6.793%   $114.7704   $114.77   $114.75   $114.80  
  Purchase #2 $154.80   3.127%   $159.6406   $159.64   $159.65   $159.60  
  Purchase #3 $244.83   5.224%   $257.6199   $257.62   $257.60   $257.60  
  Purchase #4 $30.29   4.425%   $31.6303   $31.63   $31.65   $31.60  
  Purchase #5 $232.41   6.555%   $247.6445   $247.64   $247.65   $247.60  
  Purchase #6 $209.55   5.460%   $220.9914   $220.99   $221.00   $221.00  
  Purchase #7 $65.35   5.541%   $68.971   $68.97   $68.95   $69.00  
  7 purchase totals = $1,044.70       $1,101.2681   $1,101.26   $1,101.25   $1,101.20