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 $84.39   9.320%   $92.2551   $92.26   $92.25   $92.30  
  Purchase #2 $238.95   8.662%   $259.6478   $259.65   $259.65   $259.60  
  Purchase #3 $186.78   4.423%   $195.0413   $195.04   $195.05   $195.00  
  Purchase #4 $60.48   9.112%   $65.9909   $65.99   $66.00   $66.00  
  Purchase #5 $70.30   5.249%   $73.99   $73.99   $74.00   $74.00  
  Purchase #6 $120.36   8.606%   $130.7182   $130.72   $130.70   $130.70  
  Purchase #7 $218.37   12.357%   $245.354   $245.35   $245.35   $245.40  
  7 purchase totals = $979.63       $1,062.9973   $1,063.00   $1,063.00   $1,063.00