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 $197.85   8.597%   $214.8592   $214.86   $214.85   $214.90  
  Purchase #2 $96.87   9.856%   $106.4175   $106.42   $106.40   $106.40  
  Purchase #3 $152.67   5.759%   $161.4623   $161.46   $161.45   $161.50  
  Purchase #4 $164.84   5.717%   $174.2639   $174.26   $174.25   $174.30  
  Purchase #5 $76.85   11.726%   $85.8614   $85.86   $85.85   $85.90  
  Purchase #6 $165.79   11.463%   $184.7945   $184.79   $184.80   $184.80  
  Purchase #7 $214.39   4.861%   $224.8115   $224.81   $224.80   $224.80  
  7 purchase totals = $1,069.26       $1,152.4703   $1,152.46   $1,152.40   $1,152.60