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 $176.97   8.467%   $191.954   $191.95   $191.95   $192.00  
  Purchase #2 $70.85   3.464%   $73.3042   $73.30   $73.30   $73.30  
  Purchase #3 $99.70   7.687%   $107.3639   $107.36   $107.35   $107.40  
  Purchase #4 $123.85   5.262%   $130.367   $130.37   $130.35   $130.40  
  Purchase #5 $55.45   7.852%   $59.8039   $59.80   $59.80   $59.80  
  Purchase #6 $182.99   5.284%   $192.6592   $192.66   $192.65   $192.70  
  Purchase #7 $41.71   12.657%   $46.9892   $46.99   $47.00   $47.00  
  7 purchase totals = $751.52       $802.4414   $802.43   $802.40   $802.60