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 $85.26   9.721%   $93.5481   $93.55   $93.55   $93.50  
  Purchase #2 $206.37   6.394%   $219.5653   $219.57   $219.55   $219.60  
  Purchase #3 $134.97   13.175%   $152.7523   $152.75   $152.75   $152.80  
  Purchase #4 $224.57   3.374%   $232.147   $232.15   $232.15   $232.10  
  Purchase #5 $221.27   7.696%   $238.2989   $238.30   $238.30   $238.30  
  Purchase #6 $210.27   3.862%   $218.3906   $218.39   $218.40   $218.40  
  Purchase #7 $75.87   7.344%   $81.4419   $81.44   $81.45   $81.40  
  7 purchase totals = $1,158.58       $1,236.1441   $1,236.15   $1,236.15   $1,236.10