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 $125.34   7.664%   $134.9461   $134.95   $134.95   $134.90  
  Purchase #2 $243.34   11.519%   $271.3703   $271.37   $271.35   $271.40  
  Purchase #3 $19.41   8.323%   $21.0255   $21.03   $21.05   $21.00  
  Purchase #4 $166.31   9.823%   $182.6466   $182.65   $182.65   $182.60  
  Purchase #5 $193.81   6.155%   $205.739   $205.74   $205.75   $205.70  
  Purchase #6 $152.36   10.509%   $168.3715   $168.37   $168.35   $168.40  
  Purchase #7 $71.60   6.771%   $76.448   $76.45   $76.45   $76.40  
  7 purchase totals = $972.17       $1,060.5470   $1,060.56   $1,060.55   $1,060.40