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 $237.68   10.678%   $263.0595   $263.06   $263.05   $263.10  
  Purchase #2 $232.53   11.341%   $258.9012   $258.90   $258.90   $258.90  
  Purchase #3 $198.43   6.835%   $211.9927   $211.99   $212.00   $212.00  
  Purchase #4 $71.34   13.592%   $81.0365   $81.04   $81.05   $81.00  
  Purchase #5 $79.66   7.654%   $85.7572   $85.76   $85.75   $85.80  
  Purchase #6 $112.74   12.846%   $127.2226   $127.22   $127.20   $127.20  
  Purchase #7 $121.66   3.623%   $126.0677   $126.07   $126.05   $126.10  
  7 purchase totals = $1,054.04       $1,154.0374   $1,154.04   $1,154.00   $1,154.10