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 $46.85   4.299%   $48.8641   $48.86   $48.85   $48.90  
  Purchase #2 $70.52   10.123%   $77.6587   $77.66   $77.65   $77.70  
  Purchase #3 $220.51   9.382%   $241.1982   $241.20   $241.20   $241.20  
  Purchase #4 $229.73   8.291%   $248.7769   $248.78   $248.80   $248.80  
  Purchase #5 $134.45   13.744%   $152.9288   $152.93   $152.95   $152.90  
  Purchase #6 $215.55   6.817%   $230.244   $230.24   $230.25   $230.20  
  Purchase #7 $48.90   9.170%   $53.3841   $53.38   $53.40   $53.40  
  7 purchase totals = $966.51       $1,053.0548   $1,053.05   $1,053.10   $1,053.10