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 $85.32   11.357%   $95.0098   $95.01   $95.00   $95.00  
  Purchase #2 $79.56   12.150%   $89.2265   $89.23   $89.25   $89.20  
  Purchase #3 $178.86   7.459%   $192.2012   $192.20   $192.20   $192.20  
  Purchase #4 $199.30   9.719%   $218.67   $218.67   $218.65   $218.70  
  Purchase #5 $182.83   4.126%   $190.3736   $190.37   $190.35   $190.40  
  Purchase #6 $207.67   13.449%   $235.5995   $235.60   $235.60   $235.60  
  Purchase #7 $240.71   9.493%   $263.5606   $263.56   $263.55   $263.60  
  7 purchase totals = $1,174.25       $1,284.6412   $1,284.64   $1,284.60   $1,284.70