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 $91.76   4.616%   $95.9956   $96.00   $96.00   $96.00  
  Purchase #2 $122.63   11.354%   $136.5534   $136.55   $136.55   $136.60  
  Purchase #3 $165.64   5.737%   $175.1428   $175.14   $175.15   $175.10  
  Purchase #4 $131.34   3.184%   $135.5219   $135.52   $135.50   $135.50  
  Purchase #5 $78.80   6.138%   $83.6367   $83.64   $83.65   $83.60  
  Purchase #6 $156.35   8.252%   $169.252   $169.25   $169.25   $169.30  
  Purchase #7 $221.44   8.872%   $241.0862   $241.09   $241.10   $241.10  
  7 purchase totals = $967.96       $1,037.1886   $1,037.19   $1,037.20   $1,037.20