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 $41.64   10.502%   $46.013   $46.01   $46.00   $46.00  
  Purchase #2 $76.28   13.840%   $86.8372   $86.84   $86.85   $86.80  
  Purchase #3 $74.99   3.562%   $77.6611   $77.66   $77.65   $77.70  
  Purchase #4 $110.37   10.208%   $121.6366   $121.64   $121.65   $121.60  
  Purchase #5 $218.41   5.868%   $231.2263   $231.23   $231.25   $231.20  
  Purchase #6 $87.37   10.392%   $96.4495   $96.45   $96.45   $96.40  
  Purchase #7 $240.31   10.242%   $264.9226   $264.92   $264.90   $264.90  
  7 purchase totals = $849.37       $924.7463   $924.75   $924.75   $924.60