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 $218.60   7.609%   $235.2333   $235.23   $235.25   $235.20  
  Purchase #2 $229.28   6.687%   $244.612   $244.61   $244.60   $244.60  
  Purchase #3 $94.51   7.632%   $101.723   $101.72   $101.70   $101.70  
  Purchase #4 $88.95   7.375%   $95.5101   $95.51   $95.50   $95.50  
  Purchase #5 $227.40   5.208%   $239.243   $239.24   $239.25   $239.20  
  Purchase #6 $77.94   7.420%   $83.7231   $83.72   $83.70   $83.70  
  Purchase #7 $180.25   11.525%   $201.0238   $201.02   $201.00   $201.00  
  7 purchase totals = $1,116.93       $1,201.0683   $1,201.05   $1,201.00   $1,200.90