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 $47.29   11.746%   $52.8447   $52.84   $52.85   $52.80  
  Purchase #2 $109.49   4.652%   $114.5835   $114.58   $114.60   $114.60  
  Purchase #3 $104.49   11.161%   $116.1521   $116.15   $116.15   $116.20  
  Purchase #4 $226.80   5.660%   $239.6369   $239.64   $239.65   $239.60  
  Purchase #5 $219.78   12.479%   $247.2063   $247.21   $247.20   $247.20  
  Purchase #6 $208.54   4.244%   $217.3904   $217.39   $217.40   $217.40  
  Purchase #7 $162.64   3.858%   $168.9147   $168.91   $168.90   $168.90  
  7 purchase totals = $1,079.03       $1,156.7286   $1,156.72   $1,156.75   $1,156.70