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 $69.97   5.260%   $73.6504   $73.65   $73.65   $73.70  
  Purchase #2 $211.51   7.343%   $227.0412   $227.04   $227.05   $227.00  
  Purchase #3 $82.72   8.161%   $89.4708   $89.47   $89.45   $89.50  
  Purchase #4 $208.65   12.489%   $234.7083   $234.71   $234.70   $234.70  
  Purchase #5 $47.75   5.820%   $50.5291   $50.53   $50.55   $50.50  
  Purchase #6 $211.87   11.857%   $236.9914   $236.99   $237.00   $237.00  
  Purchase #7 $203.75   4.685%   $213.2957   $213.30   $213.30   $213.30  
  7 purchase totals = $1,036.22       $1,125.6869   $1,125.69   $1,125.70   $1,125.70