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 $197.83   9.190%   $216.0106   $216.01   $216.00   $216.00  
  Purchase #2 $184.76   10.770%   $204.6587   $204.66   $204.65   $204.70  
  Purchase #3 $56.81   12.713%   $64.0323   $64.03   $64.05   $64.00  
  Purchase #4 $151.66   12.265%   $170.2611   $170.26   $170.25   $170.30  
  Purchase #5 $195.42   9.747%   $214.4676   $214.47   $214.45   $214.50  
  Purchase #6 $157.45   13.229%   $178.2791   $178.28   $178.30   $178.30  
  Purchase #7 $25.91   10.870%   $28.7264   $28.73   $28.75   $28.70  
  7 purchase totals = $969.84       $1,076.4358   $1,076.44   $1,076.45   $1,076.50