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 $148.26   13.493%   $168.2647   $168.26   $168.25   $168.30  
  Purchase #2 $149.49   7.320%   $160.4327   $160.43   $160.45   $160.40  
  Purchase #3 $102.77   9.203%   $112.2279   $112.23   $112.25   $112.20  
  Purchase #4 $206.67   7.287%   $221.73   $221.73   $221.75   $221.70  
  Purchase #5 $202.71   11.533%   $226.0885   $226.09   $226.10   $226.10  
  Purchase #6 $200.60   9.215%   $219.0853   $219.09   $219.10   $219.10  
  Purchase #7 $52.26   10.140%   $57.5592   $57.56   $57.55   $57.60  
  7 purchase totals = $1,062.76       $1,165.3883   $1,165.39   $1,165.45   $1,165.40