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 $215.90   5.855%   $228.5409   $228.54   $228.55   $228.50  
  Purchase #2 $96.46   5.768%   $102.0238   $102.02   $102.00   $102.00  
  Purchase #3 $168.70   3.655%   $174.866   $174.87   $174.85   $174.90  
  Purchase #4 $59.31   8.851%   $64.5595   $64.56   $64.55   $64.60  
  Purchase #5 $34.87   13.536%   $39.59   $39.59   $39.60   $39.60  
  Purchase #6 $68.75   12.645%   $77.4434   $77.44   $77.45   $77.40  
  Purchase #7 $83.26   4.510%   $87.015   $87.02   $87.00   $87.00  
  7 purchase totals = $727.25       $774.0386   $774.04   $774.00   $774.00