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 $87.53   9.397%   $95.7552   $95.76   $95.75   $95.80  
  Purchase #2 $221.70   11.591%   $247.3972   $247.40   $247.40   $247.40  
  Purchase #3 $159.88   8.294%   $173.1404   $173.14   $173.15   $173.10  
  Purchase #4 $160.95   9.780%   $176.6909   $176.69   $176.70   $176.70  
  Purchase #5 $95.35   10.217%   $105.0919   $105.09   $105.10   $105.10  
  Purchase #6 $129.89   13.503%   $147.429   $147.43   $147.45   $147.40  
  Purchase #7 $170.66   7.759%   $183.9015   $183.90   $183.90   $183.90  
  7 purchase totals = $1,025.96       $1,129.4061   $1,129.41   $1,129.45   $1,129.40