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 $61.58   3.868%   $63.9619   $63.96   $63.95   $64.00  
  Purchase #2 $84.87   11.520%   $94.647   $94.65   $94.65   $94.60  
  Purchase #3 $105.96   4.160%   $110.3679   $110.37   $110.35   $110.40  
  Purchase #4 $180.72   13.471%   $205.0648   $205.06   $205.05   $205.10  
  Purchase #5 $203.86   4.720%   $213.4822   $213.48   $213.50   $213.50  
  Purchase #6 $85.92   10.326%   $94.7921   $94.79   $94.80   $94.80  
  Purchase #7 $81.95   5.406%   $86.3802   $86.38   $86.40   $86.40  
  7 purchase totals = $804.86       $868.6961   $868.69   $868.70   $868.80