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 $211.29   12.207%   $237.0822   $237.08   $237.10   $237.10  
  Purchase #2 $243.98   10.257%   $269.005   $269.01   $269.00   $269.00  
  Purchase #3 $46.66   13.404%   $52.9143   $52.91   $52.90   $52.90  
  Purchase #4 $229.90   13.779%   $261.5779   $261.58   $261.60   $261.60  
  Purchase #5 $214.29   4.689%   $224.3381   $224.34   $224.35   $224.30  
  Purchase #6 $195.36   3.396%   $201.9944   $201.99   $202.00   $202.00  
  Purchase #7 $17.76   5.305%   $18.7022   $18.70   $18.70   $18.70  
  7 purchase totals = $1,159.24       $1,265.6141   $1,265.61   $1,265.65   $1,265.60