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 $87.88   8.830%   $95.6398   $95.64   $95.65   $95.60  
  Purchase #2 $52.36   10.173%   $57.6866   $57.69   $57.70   $57.70  
  Purchase #3 $126.41   11.712%   $141.2151   $141.22   $141.20   $141.20  
  Purchase #4 $132.60   6.767%   $141.573   $141.57   $141.55   $141.60  
  Purchase #5 $57.51   10.766%   $63.7015   $63.70   $63.70   $63.70  
  Purchase #6 $232.36   11.467%   $259.0047   $259.00   $259.00   $259.00  
  Purchase #7 $113.79   9.532%   $124.6365   $124.64   $124.65   $124.60  
  7 purchase totals = $802.91       $883.4572   $883.46   $883.45   $883.40