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 $67.44   8.609%   $73.2459   $73.25   $73.25   $73.20  
  Purchase #2 $217.92   3.378%   $225.2813   $225.28   $225.30   $225.30  
  Purchase #3 $176.51   3.154%   $182.0771   $182.08   $182.10   $182.10  
  Purchase #4 $153.32   3.631%   $158.887   $158.89   $158.90   $158.90  
  Purchase #5 $134.81   6.451%   $143.5066   $143.51   $143.50   $143.50  
  Purchase #6 $169.29   12.407%   $190.2938   $190.29   $190.30   $190.30  
  Purchase #7 $219.31   11.504%   $244.5394   $244.54   $244.55   $244.50  
  7 purchase totals = $1,138.60       $1,217.8311   $1,217.84   $1,217.90   $1,217.80