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 $191.53   12.124%   $214.7511   $214.75   $214.75   $214.80  
  Purchase #2 $40.72   4.268%   $42.4579   $42.46   $42.45   $42.50  
  Purchase #3 $234.32   5.284%   $246.7015   $246.70   $246.70   $246.70  
  Purchase #4 $103.45   13.646%   $117.5668   $117.57   $117.55   $117.60  
  Purchase #5 $249.44   12.615%   $280.9069   $280.91   $280.90   $280.90  
  Purchase #6 $73.66   3.283%   $76.0783   $76.08   $76.10   $76.10  
  Purchase #7 $169.86   11.560%   $189.4958   $189.50   $189.50   $189.50  
  7 purchase totals = $1,062.98       $1,167.9583   $1,167.97   $1,167.95   $1,168.10