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 $84.61   13.684%   $96.188   $96.19   $96.20   $96.20  
  Purchase #2 $89.25   4.158%   $92.961   $92.96   $92.95   $93.00  
  Purchase #3 $43.58   10.695%   $48.2409   $48.24   $48.25   $48.20  
  Purchase #4 $155.26   9.481%   $169.9802   $169.98   $170.00   $170.00  
  Purchase #5 $172.83   9.598%   $189.4182   $189.42   $189.40   $189.40  
  Purchase #6 $217.29   8.727%   $236.2529   $236.25   $236.25   $236.30  
  Purchase #7 $28.30   8.477%   $30.699   $30.70   $30.70   $30.70  
  7 purchase totals = $791.12       $863.7402   $863.74   $863.75   $863.80