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 $212.71   10.722%   $235.5168   $235.52   $235.50   $235.50  
  Purchase #2 $236.82   4.874%   $248.3626   $248.36   $248.35   $248.40  
  Purchase #3 $24.84   7.237%   $26.6377   $26.64   $26.65   $26.60  
  Purchase #4 $46.66   4.612%   $48.812   $48.81   $48.80   $48.80  
  Purchase #5 $82.67   6.187%   $87.7848   $87.78   $87.80   $87.80  
  Purchase #6 $147.53   12.689%   $166.2501   $166.25   $166.25   $166.30  
  Purchase #7 $213.93   10.490%   $236.3713   $236.37   $236.35   $236.40  
  7 purchase totals = $965.16       $1,049.7353   $1,049.73   $1,049.70   $1,049.80