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 $191.60   10.472%   $211.6644   $211.66   $211.65   $211.70  
  Purchase #2 $224.26   13.172%   $253.7995   $253.80   $253.80   $253.80  
  Purchase #3 $192.59   8.553%   $209.0622   $209.06   $209.05   $209.10  
  Purchase #4 $87.64   7.542%   $94.2498   $94.25   $94.25   $94.20  
  Purchase #5 $114.91   9.809%   $126.1815   $126.18   $126.20   $126.20  
  Purchase #6 $59.55   4.545%   $62.2565   $62.26   $62.25   $62.30  
  Purchase #7 $8.31   5.797%   $8.7917   $8.79   $8.80   $8.80  
  7 purchase totals = $878.86       $966.0056   $966.00   $966.00   $966.10