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 $174.29   11.297%   $193.9795   $193.98   $194.00   $194.00  
  Purchase #2 $121.54   4.246%   $126.7006   $126.70   $126.70   $126.70  
  Purchase #3 $50.62   9.736%   $55.5484   $55.55   $55.55   $55.50  
  Purchase #4 $5.99   9.710%   $6.5716   $6.57   $6.55   $6.60  
  Purchase #5 $248.29   11.448%   $276.7142   $276.71   $276.70   $276.70  
  Purchase #6 $187.85   9.380%   $205.4703   $205.47   $205.45   $205.50  
  Purchase #7 $164.47   8.827%   $178.9878   $178.99   $179.00   $179.00  
  7 purchase totals = $953.05       $1,043.9724   $1,043.97   $1,043.95   $1,044.00