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 $55.81   8.756%   $60.6967   $60.70   $60.70   $60.70  
  Purchase #2 $192.94   11.428%   $214.9892   $214.99   $215.00   $215.00  
  Purchase #3 $178.69   9.187%   $195.1063   $195.11   $195.10   $195.10  
  Purchase #4 $174.62   3.706%   $181.0914   $181.09   $181.10   $181.10  
  Purchase #5 $176.65   12.810%   $199.2789   $199.28   $199.30   $199.30  
  Purchase #6 $176.62   8.688%   $191.9647   $191.96   $191.95   $192.00  
  Purchase #7 $21.25   12.259%   $23.855   $23.86   $23.85   $23.90  
  7 purchase totals = $976.58       $1,066.9822   $1,066.99   $1,067.00   $1,067.10