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 $33.37   7.836%   $35.9849   $35.98   $36.00   $36.00  
  Purchase #2 $148.70   3.102%   $153.3127   $153.31   $153.30   $153.30  
  Purchase #3 $71.56   11.274%   $79.6277   $79.63   $79.65   $79.60  
  Purchase #4 $136.67   9.443%   $149.5757   $149.58   $149.60   $149.60  
  Purchase #5 $181.90   6.274%   $193.3124   $193.31   $193.30   $193.30  
  Purchase #6 $200.58   4.662%   $209.931   $209.93   $209.95   $209.90  
  Purchase #7 $117.71   6.482%   $125.34   $125.34   $125.35   $125.30  
  7 purchase totals = $890.49       $947.0844   $947.08   $947.15   $947.00