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 $205.88   13.431%   $233.5317   $233.53   $233.55   $233.50  
  Purchase #2 $180.79   4.254%   $188.4808   $188.48   $188.50   $188.50  
  Purchase #3 $196.49   3.146%   $202.6716   $202.67   $202.65   $202.70  
  Purchase #4 $58.76   7.536%   $63.1882   $63.19   $63.20   $63.20  
  Purchase #5 $199.25   6.389%   $211.9801   $211.98   $212.00   $212.00  
  Purchase #6 $164.55   7.501%   $176.8929   $176.89   $176.90   $176.90  
  Purchase #7 $121.42   5.833%   $128.5024   $128.50   $128.50   $128.50  
  7 purchase totals = $1,127.14       $1,205.2477   $1,205.24   $1,205.30   $1,205.30