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 $223.97   3.614%   $232.0643   $232.06   $232.05   $232.10  
  Purchase #2 $208.81   12.207%   $234.2994   $234.30   $234.30   $234.30  
  Purchase #3 $156.56   12.195%   $175.6525   $175.65   $175.65   $175.70  
  Purchase #4 $137.42   10.538%   $151.9013   $151.90   $151.90   $151.90  
  Purchase #5 $65.68   3.447%   $67.944   $67.94   $67.95   $67.90  
  Purchase #6 $26.72   5.117%   $28.0873   $28.09   $28.10   $28.10  
  Purchase #7 $181.36   11.793%   $202.7478   $202.75   $202.75   $202.70  
  7 purchase totals = $1,000.52       $1,092.6966   $1,092.69   $1,092.70   $1,092.70