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 $39.74   8.239%   $43.0142   $43.01   $43.00   $43.00  
  Purchase #2 $228.48   13.450%   $259.2106   $259.21   $259.20   $259.20  
  Purchase #3 $32.55   7.438%   $34.9711   $34.97   $34.95   $35.00  
  Purchase #4 $166.88   7.414%   $179.2525   $179.25   $179.25   $179.30  
  Purchase #5 $181.70   5.103%   $190.9722   $190.97   $190.95   $191.00  
  Purchase #6 $60.96   11.480%   $67.9582   $67.96   $67.95   $68.00  
  Purchase #7 $161.84   4.454%   $169.0484   $169.05   $169.05   $169.00  
  7 purchase totals = $872.15       $944.4272   $944.42   $944.35   $944.50