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 $209.88   11.141%   $233.2627   $233.26   $233.25   $233.30  
  Purchase #2 $60.76   11.587%   $67.8003   $67.80   $67.80   $67.80  
  Purchase #3 $247.57   6.246%   $263.0332   $263.03   $263.05   $263.00  
  Purchase #4 $102.73   6.155%   $109.053   $109.05   $109.05   $109.10  
  Purchase #5 $187.45   5.652%   $198.0447   $198.04   $198.05   $198.00  
  Purchase #6 $97.62   10.658%   $108.0243   $108.02   $108.00   $108.00  
  Purchase #7 $43.46   8.200%   $47.0237   $47.02   $47.00   $47.00  
  7 purchase totals = $949.47       $1,026.2419   $1,026.22   $1,026.20   $1,026.20