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 $71.45   7.526%   $76.8273   $76.83   $76.85   $76.80  
  Purchase #2 $169.93   11.259%   $189.0624   $189.06   $189.05   $189.10  
  Purchase #3 $50.63   13.565%   $57.498   $57.50   $57.50   $57.50  
  Purchase #4 $142.33   9.614%   $156.0136   $156.01   $156.00   $156.00  
  Purchase #5 $154.28   5.232%   $162.3519   $162.35   $162.35   $162.40  
  Purchase #6 $214.69   13.525%   $243.7268   $243.73   $243.75   $243.70  
  Purchase #7 $31.64   6.870%   $33.8137   $33.81   $33.80   $33.80  
  7 purchase totals = $834.95       $919.2937   $919.29   $919.30   $919.30