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 $117.64   5.154%   $123.7032   $123.70   $123.70   $123.70  
  Purchase #2 $243.93   8.765%   $265.3105   $265.31   $265.30   $265.30  
  Purchase #3 $211.35   8.129%   $228.5306   $228.53   $228.55   $228.50  
  Purchase #4 $232.96   11.367%   $259.4406   $259.44   $259.45   $259.40  
  Purchase #5 $151.70   6.493%   $161.5499   $161.55   $161.55   $161.50  
  Purchase #6 $243.42   6.803%   $259.9799   $259.98   $260.00   $260.00  
  Purchase #7 $159.86   8.727%   $173.811   $173.81   $173.80   $173.80  
  7 purchase totals = $1,360.86       $1,472.3257   $1,472.32   $1,472.35   $1,472.20