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 $5.50   7.651%   $5.9208   $5.92   $5.90   $5.90  
  Purchase #2 $220.26   11.261%   $245.0635   $245.06   $245.05   $245.10  
  Purchase #3 $66.50   6.671%   $70.9362   $70.94   $70.95   $70.90  
  Purchase #4 $174.52   8.609%   $189.5444   $189.54   $189.55   $189.50  
  Purchase #5 $198.75   6.416%   $211.5018   $211.50   $211.50   $211.50  
  Purchase #6 $212.99   11.138%   $236.7128   $236.71   $236.70   $236.70  
  Purchase #7 $131.35   3.477%   $135.917   $135.92   $135.90   $135.90  
  7 purchase totals = $1,009.87       $1,095.5965   $1,095.59   $1,095.55   $1,095.50