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 $46.31   13.444%   $52.5359   $52.54   $52.55   $52.50  
  Purchase #2 $225.81   4.797%   $236.6421   $236.64   $236.65   $236.60  
  Purchase #3 $187.47   11.294%   $208.6429   $208.64   $208.65   $208.60  
  Purchase #4 $94.92   9.332%   $103.7779   $103.78   $103.80   $103.80  
  Purchase #5 $97.56   7.667%   $105.0399   $105.04   $105.05   $105.00  
  Purchase #6 $211.28   6.265%   $224.5167   $224.52   $224.50   $224.50  
  Purchase #7 $243.57   11.616%   $271.8631   $271.86   $271.85   $271.90  
  7 purchase totals = $1,106.92       $1,203.0185   $1,203.02   $1,203.05   $1,202.90