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 $22.99   11.292%   $25.586   $25.59   $25.60   $25.60  
  Purchase #2 $113.65   4.821%   $119.1291   $119.13   $119.15   $119.10  
  Purchase #3 $157.88   9.856%   $173.4407   $173.44   $173.45   $173.40  
  Purchase #4 $23.39   9.251%   $25.5538   $25.55   $25.55   $25.60  
  Purchase #5 $202.88   13.865%   $231.0093   $231.01   $231.00   $231.00  
  Purchase #6 $205.56   4.493%   $214.7958   $214.80   $214.80   $214.80  
  Purchase #7 $211.32   7.780%   $227.7607   $227.76   $227.75   $227.80  
  7 purchase totals = $937.67       $1,017.2754   $1,017.28   $1,017.30   $1,017.30