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 $243.35   7.760%   $262.234   $262.23   $262.25   $262.20  
  Purchase #2 $9.65   4.844%   $10.1174   $10.12   $10.10   $10.10  
  Purchase #3 $21.66   9.701%   $23.7612   $23.76   $23.75   $23.80  
  Purchase #4 $164.82   12.419%   $185.289   $185.29   $185.30   $185.30  
  Purchase #5 $242.40   5.166%   $254.9224   $254.92   $254.90   $254.90  
  Purchase #6 $174.86   4.830%   $183.3057   $183.31   $183.30   $183.30  
  Purchase #7 $118.74   12.869%   $134.0207   $134.02   $134.00   $134.00  
  7 purchase totals = $975.48       $1,053.6504   $1,053.65   $1,053.60   $1,053.60