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 $217.34   9.820%   $238.6828   $238.68   $238.70   $238.70  
  Purchase #2 $117.26   8.866%   $127.6563   $127.66   $127.65   $127.70  
  Purchase #3 $77.70   13.219%   $87.9712   $87.97   $87.95   $88.00  
  Purchase #4 $63.28   13.469%   $71.8032   $71.80   $71.80   $71.80  
  Purchase #5 $195.63   6.596%   $208.5338   $208.53   $208.55   $208.50  
  Purchase #6 $180.72   5.744%   $191.1006   $191.10   $191.10   $191.10  
  Purchase #7 $155.62   9.255%   $170.0226   $170.02   $170.00   $170.00  
  7 purchase totals = $1,007.55       $1,095.7705   $1,095.76   $1,095.75   $1,095.80