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 $49.48   5.217%   $52.0614   $52.06   $52.05   $52.10  
  Purchase #2 $105.59   10.854%   $117.0507   $117.05   $117.05   $117.10  
  Purchase #3 $164.33   4.252%   $171.3173   $171.32   $171.30   $171.30  
  Purchase #4 $19.66   12.258%   $22.0699   $22.07   $22.05   $22.10  
  Purchase #5 $19.67   13.810%   $22.3864   $22.39   $22.40   $22.40  
  Purchase #6 $94.90   12.784%   $107.032   $107.03   $107.05   $107.00  
  Purchase #7 $241.48   7.807%   $260.3323   $260.33   $260.35   $260.30  
  7 purchase totals = $695.11       $752.2500   $752.25   $752.25   $752.30