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 $41.73   5.558%   $44.0494   $44.05   $44.05   $44.00  
  Purchase #2 $74.74   6.605%   $79.6766   $79.68   $79.70   $79.70  
  Purchase #3 $174.88   5.429%   $184.3742   $184.37   $184.35   $184.40  
  Purchase #4 $226.25   9.278%   $247.2415   $247.24   $247.25   $247.20  
  Purchase #5 $198.25   13.699%   $225.4083   $225.41   $225.40   $225.40  
  Purchase #6 $183.62   10.605%   $203.0929   $203.09   $203.10   $203.10  
  Purchase #7 $209.30   4.768%   $219.2794   $219.28   $219.30   $219.30  
  7 purchase totals = $1,108.77       $1,203.1223   $1,203.12   $1,203.15   $1,203.10