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 $94.90   3.527%   $98.2471   $98.25   $98.25   $98.20  
  Purchase #2 $232.51   7.338%   $249.5716   $249.57   $249.55   $249.60  
  Purchase #3 $111.71   5.497%   $117.8507   $117.85   $117.85   $117.90  
  Purchase #4 $187.61   11.275%   $208.763   $208.76   $208.75   $208.80  
  Purchase #5 $25.72   3.435%   $26.6035   $26.60   $26.60   $26.60  
  Purchase #6 $161.61   13.172%   $182.8973   $182.90   $182.90   $182.90  
  Purchase #7 $150.94   9.335%   $165.0302   $165.03   $165.05   $165.00  
  7 purchase totals = $965.00       $1,048.9634   $1,048.96   $1,048.95   $1,049.00