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 $62.76   5.248%   $66.0536   $66.05   $66.05   $66.10  
  Purchase #2 $23.33   8.424%   $25.2953   $25.30   $25.30   $25.30  
  Purchase #3 $157.94   5.436%   $166.5256   $166.53   $166.55   $166.50  
  Purchase #4 $185.82   12.473%   $208.9973   $209.00   $209.00   $209.00  
  Purchase #5 $53.91   5.137%   $56.6794   $56.68   $56.70   $56.70  
  Purchase #6 $185.85   10.319%   $205.0279   $205.03   $205.05   $205.00  
  Purchase #7 $214.33   8.162%   $231.8236   $231.82   $231.80   $231.80  
  7 purchase totals = $883.94       $960.4027   $960.41   $960.45   $960.40