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 $242.92   10.718%   $268.9562   $268.96   $268.95   $269.00  
  Purchase #2 $174.31   9.658%   $191.1449   $191.14   $191.15   $191.10  
  Purchase #3 $39.73   5.757%   $42.0173   $42.02   $42.00   $42.00  
  Purchase #4 $60.66   10.781%   $67.1998   $67.20   $67.20   $67.20  
  Purchase #5 $177.59   8.267%   $192.2714   $192.27   $192.25   $192.30  
  Purchase #6 $233.74   9.494%   $255.9313   $255.93   $255.95   $255.90  
  Purchase #7 $91.65   3.577%   $94.9283   $94.93   $94.95   $94.90  
  7 purchase totals = $1,020.60       $1,112.4492   $1,112.45   $1,112.45   $1,112.40