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 $70.87   8.662%   $77.0088   $77.01   $77.00   $77.00  
  Purchase #2 $234.85   6.664%   $250.5004   $250.50   $250.50   $250.50  
  Purchase #3 $111.43   13.753%   $126.755   $126.76   $126.75   $126.80  
  Purchase #4 $98.52   3.589%   $102.0559   $102.06   $102.05   $102.10  
  Purchase #5 $148.61   6.396%   $158.1151   $158.12   $158.10   $158.10  
  Purchase #6 $73.62   10.866%   $81.6195   $81.62   $81.60   $81.60  
  Purchase #7 $202.62   6.207%   $215.1966   $215.20   $215.20   $215.20  
  7 purchase totals = $940.52       $1,011.2513   $1,011.27   $1,011.20   $1,011.30