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 $196.79   4.318%   $205.2874   $205.29   $205.30   $205.30  
  Purchase #2 $46.89   9.234%   $51.2198   $51.22   $51.20   $51.20  
  Purchase #3 $77.96   11.488%   $86.916   $86.92   $86.90   $86.90  
  Purchase #4 $209.37   12.740%   $236.0437   $236.04   $236.05   $236.00  
  Purchase #5 $166.26   13.547%   $188.7832   $188.78   $188.80   $188.80  
  Purchase #6 $68.72   6.403%   $73.1201   $73.12   $73.10   $73.10  
  Purchase #7 $248.37   6.777%   $265.202   $265.20   $265.20   $265.20  
  7 purchase totals = $1,014.36       $1,106.5722   $1,106.57   $1,106.55   $1,106.50