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 $94.52   10.743%   $104.6743   $104.67   $104.65   $104.70  
  Purchase #2 $159.88   8.508%   $173.4826   $173.48   $173.50   $173.50  
  Purchase #3 $38.74   11.685%   $43.2668   $43.27   $43.25   $43.30  
  Purchase #4 $130.40   3.128%   $134.4789   $134.48   $134.50   $134.50  
  Purchase #5 $87.86   4.681%   $91.9727   $91.97   $91.95   $92.00  
  Purchase #6 $58.88   7.413%   $63.2448   $63.24   $63.25   $63.20  
  Purchase #7 $127.49   3.153%   $131.5098   $131.51   $131.50   $131.50  
  7 purchase totals = $697.77       $742.6299   $742.62   $742.60   $742.70