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 $23.88   11.195%   $26.5534   $26.55   $26.55   $26.60  
  Purchase #2 $209.25   9.628%   $229.3966   $229.40   $229.40   $229.40  
  Purchase #3 $210.91   10.305%   $232.6443   $232.64   $232.65   $232.60  
  Purchase #4 $103.89   12.111%   $116.4721   $116.47   $116.45   $116.50  
  Purchase #5 $31.28   7.387%   $33.5907   $33.59   $33.60   $33.60  
  Purchase #6 $231.98   3.662%   $240.4751   $240.48   $240.50   $240.50  
  Purchase #7 $216.46   4.694%   $226.6206   $226.62   $226.60   $226.60  
  7 purchase totals = $1,027.65       $1,105.7528   $1,105.75   $1,105.75   $1,105.80