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 $104.36   3.691%   $108.2119   $108.21   $108.20   $108.20  
  Purchase #2 $161.95   8.280%   $175.3595   $175.36   $175.35   $175.40  
  Purchase #3 $157.79   7.136%   $169.0499   $169.05   $169.05   $169.00  
  Purchase #4 $220.43   4.379%   $230.0826   $230.08   $230.10   $230.10  
  Purchase #5 $164.41   8.194%   $177.8818   $177.88   $177.90   $177.90  
  Purchase #6 $165.72   10.667%   $183.3974   $183.40   $183.40   $183.40  
  Purchase #7 $60.55   3.612%   $62.7371   $62.74   $62.75   $62.70  
  7 purchase totals = $1,035.21       $1,106.7202   $1,106.72   $1,106.75   $1,106.70