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 $186.27   8.427%   $201.967   $201.97   $201.95   $202.00  
  Purchase #2 $59.25   5.752%   $62.6581   $62.66   $62.65   $62.70  
  Purchase #3 $91.30   5.651%   $96.4594   $96.46   $96.45   $96.50  
  Purchase #4 $232.63   12.653%   $262.0647   $262.06   $262.05   $262.10  
  Purchase #5 $76.57   5.171%   $80.5294   $80.53   $80.55   $80.50  
  Purchase #6 $147.33   9.631%   $161.5194   $161.52   $161.50   $161.50  
  Purchase #7 $114.82   6.540%   $122.3292   $122.33   $122.35   $122.30  
  7 purchase totals = $908.17       $987.5272   $987.53   $987.50   $987.60