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 $96.61   8.610%   $104.9281   $104.93   $104.95   $104.90  
  Purchase #2 $28.96   13.226%   $32.7902   $32.79   $32.80   $32.80  
  Purchase #3 $207.91   10.270%   $229.2624   $229.26   $229.25   $229.30  
  Purchase #4 $147.82   5.642%   $156.16   $156.16   $156.15   $156.20  
  Purchase #5 $156.59   4.667%   $163.8981   $163.90   $163.90   $163.90  
  Purchase #6 $249.99   13.379%   $283.4362   $283.44   $283.45   $283.40  
  Purchase #7 $180.35   5.644%   $190.529   $190.53   $190.55   $190.50  
  7 purchase totals = $1,068.23       $1,161.0040   $1,161.01   $1,161.05   $1,161.00