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 $86.69   9.139%   $94.6126   $94.61   $94.60   $94.60  
  Purchase #2 $170.77   6.340%   $181.5968   $181.60   $181.60   $181.60  
  Purchase #3 $208.30   10.443%   $230.0528   $230.05   $230.05   $230.10  
  Purchase #4 $148.85   3.833%   $154.5554   $154.56   $154.55   $154.60  
  Purchase #5 $109.38   4.777%   $114.6051   $114.61   $114.60   $114.60  
  Purchase #6 $163.53   10.240%   $180.2755   $180.28   $180.30   $180.30  
  Purchase #7 $108.62   10.813%   $120.3651   $120.37   $120.35   $120.40  
  7 purchase totals = $996.14       $1,076.0633   $1,076.08   $1,076.05   $1,076.20