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 $82.27   5.463%   $86.7644   $86.76   $86.75   $86.80  
  Purchase #2 $112.49   4.332%   $117.3631   $117.36   $117.35   $117.40  
  Purchase #3 $54.56   10.484%   $60.2801   $60.28   $60.30   $60.30  
  Purchase #4 $20.54   5.469%   $21.6633   $21.66   $21.65   $21.70  
  Purchase #5 $40.70   11.769%   $45.49   $45.49   $45.50   $45.50  
  Purchase #6 $224.79   3.122%   $231.8079   $231.81   $231.80   $231.80  
  Purchase #7 $166.63   6.627%   $177.6726   $177.67   $177.65   $177.70  
  7 purchase totals = $701.98       $741.0414   $741.03   $741.00   $741.20