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 $104.87   8.686%   $113.979   $113.98   $114.00   $114.00  
  Purchase #2 $180.62   11.864%   $202.0488   $202.05   $202.05   $202.00  
  Purchase #3 $99.26   8.703%   $107.8986   $107.90   $107.90   $107.90  
  Purchase #4 $153.97   13.828%   $175.261   $175.26   $175.25   $175.30  
  Purchase #5 $208.95   7.636%   $224.9054   $224.91   $224.90   $224.90  
  Purchase #6 $187.52   9.797%   $205.8913   $205.89   $205.90   $205.90  
  Purchase #7 $134.46   10.340%   $148.3632   $148.36   $148.35   $148.40  
  7 purchase totals = $1,069.65       $1,178.3473   $1,178.35   $1,178.35   $1,178.40