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 $248.67   5.599%   $262.593   $262.59   $262.60   $262.60  
  Purchase #2 $5.38   8.350%   $5.8292   $5.83   $5.85   $5.80  
  Purchase #3 $193.94   3.645%   $201.0091   $201.01   $201.00   $201.00  
  Purchase #4 $97.55   5.362%   $102.7806   $102.78   $102.80   $102.80  
  Purchase #5 $44.87   3.232%   $46.3202   $46.32   $46.30   $46.30  
  Purchase #6 $246.25   10.295%   $271.6014   $271.60   $271.60   $271.60  
  Purchase #7 $133.64   6.523%   $142.3573   $142.36   $142.35   $142.40  
  7 purchase totals = $970.30       $1,032.4908   $1,032.49   $1,032.50   $1,032.50