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 $92.28   3.290%   $95.316   $95.32   $95.30   $95.30  
  Purchase #2 $159.74   5.651%   $168.7669   $168.77   $168.75   $168.80  
  Purchase #3 $139.29   8.434%   $151.0377   $151.04   $151.05   $151.00  
  Purchase #4 $115.57   3.102%   $119.155   $119.16   $119.15   $119.20  
  Purchase #5 $245.73   8.228%   $265.9487   $265.95   $265.95   $265.90  
  Purchase #6 $141.34   10.686%   $156.4436   $156.44   $156.45   $156.40  
  Purchase #7 $231.25   6.822%   $247.0259   $247.03   $247.05   $247.00  
  7 purchase totals = $1,125.20       $1,203.6938   $1,203.71   $1,203.70   $1,203.60