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 $69.58   10.636%   $76.9805   $76.98   $77.00   $77.00  
  Purchase #2 $186.57   4.751%   $195.4339   $195.43   $195.45   $195.40  
  Purchase #3 $55.76   4.819%   $58.4471   $58.45   $58.45   $58.40  
  Purchase #4 $169.41   5.235%   $178.2786   $178.28   $178.30   $178.30  
  Purchase #5 $178.43   13.535%   $202.5805   $202.58   $202.60   $202.60  
  Purchase #6 $28.77   11.233%   $32.0017   $32.00   $32.00   $32.00  
  Purchase #7 $234.47   7.463%   $251.9685   $251.97   $251.95   $252.00  
  7 purchase totals = $922.99       $995.6908   $995.69   $995.75   $995.70