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 $228.95   3.111%   $236.0726   $236.07   $236.05   $236.10  
  Purchase #2 $236.32   12.712%   $266.361   $266.36   $266.35   $266.40  
  Purchase #3 $55.71   4.214%   $58.0576   $58.06   $58.05   $58.10  
  Purchase #4 $169.35   5.286%   $178.3018   $178.30   $178.30   $178.30  
  Purchase #5 $168.56   9.560%   $184.6743   $184.67   $184.65   $184.70  
  Purchase #6 $84.97   8.478%   $92.1738   $92.17   $92.15   $92.20  
  Purchase #7 $44.26   5.377%   $46.6399   $46.64   $46.65   $46.60  
  7 purchase totals = $988.12       $1,062.2810   $1,062.27   $1,062.20   $1,062.40