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 $119.67   12.725%   $134.898   $134.90   $134.90   $134.90  
  Purchase #2 $44.40   8.104%   $47.9982   $48.00   $48.00   $48.00  
  Purchase #3 $106.88   6.556%   $113.8871   $113.89   $113.90   $113.90  
  Purchase #4 $65.64   6.339%   $69.8009   $69.80   $69.80   $69.80  
  Purchase #5 $219.29   5.833%   $232.0812   $232.08   $232.10   $232.10  
  Purchase #6 $228.95   9.780%   $251.3413   $251.34   $251.35   $251.30  
  Purchase #7 $228.66   10.758%   $253.2592   $253.26   $253.25   $253.30  
  7 purchase totals = $1,013.49       $1,103.2659   $1,103.27   $1,103.30   $1,103.30