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 $174.65   11.230%   $194.2632   $194.26   $194.25   $194.30  
  Purchase #2 $65.92   7.860%   $71.1013   $71.10   $71.10   $71.10  
  Purchase #3 $219.46   3.705%   $227.591   $227.59   $227.60   $227.60  
  Purchase #4 $32.58   8.868%   $35.4692   $35.47   $35.45   $35.50  
  Purchase #5 $234.97   10.490%   $259.6184   $259.62   $259.60   $259.60  
  Purchase #6 $122.40   6.485%   $130.3376   $130.34   $130.35   $130.30  
  Purchase #7 $168.42   5.348%   $177.4271   $177.43   $177.45   $177.40  
  7 purchase totals = $1,018.40       $1,095.8078   $1,095.81   $1,095.80   $1,095.80