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 $88.47   8.479%   $95.9714   $95.97   $95.95   $96.00  
  Purchase #2 $114.82   6.264%   $122.0123   $122.01   $122.00   $122.00  
  Purchase #3 $96.66   6.655%   $103.0927   $103.09   $103.10   $103.10  
  Purchase #4 $160.46   9.599%   $175.8626   $175.86   $175.85   $175.90  
  Purchase #5 $146.33   13.344%   $165.8563   $165.86   $165.85   $165.90  
  Purchase #6 $83.82   5.250%   $88.2206   $88.22   $88.20   $88.20  
  Purchase #7 $106.29   3.139%   $109.6264   $109.63   $109.65   $109.60  
  7 purchase totals = $796.85       $860.6423   $860.64   $860.60   $860.70