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 $61.61   13.193%   $69.7382   $69.74   $69.75   $69.70  
  Purchase #2 $242.62   9.685%   $266.1177   $266.12   $266.10   $266.10  
  Purchase #3 $117.44   9.371%   $128.4453   $128.45   $128.45   $128.40  
  Purchase #4 $145.61   12.757%   $164.1855   $164.19   $164.20   $164.20  
  Purchase #5 $135.49   8.629%   $147.1814   $147.18   $147.20   $147.20  
  Purchase #6 $164.99   10.648%   $182.5581   $182.56   $182.55   $182.60  
  Purchase #7 $227.37   3.136%   $234.5003   $234.50   $234.50   $234.50  
  7 purchase totals = $1,095.13       $1,192.7265   $1,192.74   $1,192.75   $1,192.70