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 $62.92   6.513%   $67.018   $67.02   $67.00   $67.00  
  Purchase #2 $237.33   13.260%   $268.8   $268.80   $268.80   $268.80  
  Purchase #3 $161.50   3.329%   $166.8763   $166.88   $166.90   $166.90  
  Purchase #4 $177.83   10.368%   $196.2674   $196.27   $196.25   $196.30  
  Purchase #5 $38.43   11.125%   $42.7053   $42.71   $42.70   $42.70  
  Purchase #6 $20.64   11.348%   $22.9822   $22.98   $23.00   $23.00  
  Purchase #7 $88.43   7.757%   $95.2895   $95.29   $95.30   $95.30  
  7 purchase totals = $787.08       $859.9387   $859.95   $859.95   $860.00