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 $74.84   4.185%   $77.9721   $77.97   $77.95   $78.00  
  Purchase #2 $174.69   4.392%   $182.3624   $182.36   $182.35   $182.40  
  Purchase #3 $232.80   4.243%   $242.6777   $242.68   $242.70   $242.70  
  Purchase #4 $26.76   11.246%   $29.7694   $29.77   $29.75   $29.80  
  Purchase #5 $233.58   11.365%   $260.1264   $260.13   $260.15   $260.10  
  Purchase #6 $118.76   8.644%   $129.0256   $129.03   $129.05   $129.00  
  Purchase #7 $69.30   5.403%   $73.0443   $73.04   $73.05   $73.00  
  7 purchase totals = $930.73       $994.9779   $994.98   $995.00   $995.00