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 $32.51   8.329%   $35.2178   $35.22   $35.20   $35.20  
  Purchase #2 $224.30   3.366%   $231.8499   $231.85   $231.85   $231.80  
  Purchase #3 $88.81   7.300%   $95.2931   $95.29   $95.30   $95.30  
  Purchase #4 $106.69   10.567%   $117.9639   $117.96   $117.95   $118.00  
  Purchase #5 $196.66   8.516%   $213.4076   $213.41   $213.40   $213.40  
  Purchase #6 $235.81   12.472%   $265.2202   $265.22   $265.20   $265.20  
  Purchase #7 $200.74   3.785%   $208.338   $208.34   $208.35   $208.30  
  7 purchase totals = $1,085.52       $1,167.2905   $1,167.29   $1,167.25   $1,167.20