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 $214.66   4.604%   $224.5429   $224.54   $224.55   $224.50  
  Purchase #2 $177.99   10.320%   $196.3586   $196.36   $196.35   $196.40  
  Purchase #3 $185.59   11.808%   $207.5045   $207.50   $207.50   $207.50  
  Purchase #4 $203.48   12.521%   $228.9577   $228.96   $228.95   $229.00  
  Purchase #5 $201.78   8.133%   $218.1908   $218.19   $218.20   $218.20  
  Purchase #6 $58.42   3.331%   $60.366   $60.37   $60.35   $60.40  
  Purchase #7 $162.88   10.358%   $179.7511   $179.75   $179.75   $179.80  
  7 purchase totals = $1,204.80       $1,315.6716   $1,315.67   $1,315.65   $1,315.80