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 $207.39   9.841%   $227.7992   $227.80   $227.80   $227.80  
  Purchase #2 $217.80   6.383%   $231.7022   $231.70   $231.70   $231.70  
  Purchase #3 $52.58   11.842%   $58.8065   $58.81   $58.80   $58.80  
  Purchase #4 $163.57   11.586%   $182.5212   $182.52   $182.50   $182.50  
  Purchase #5 $210.36   8.813%   $228.899   $228.90   $228.90   $228.90  
  Purchase #6 $192.91   10.620%   $213.397   $213.40   $213.40   $213.40  
  Purchase #7 $33.55   7.558%   $36.0857   $36.09   $36.10   $36.10  
  7 purchase totals = $1,078.16       $1,179.2108   $1,179.22   $1,179.20   $1,179.20