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 $173.57   12.699%   $195.6117   $195.61   $195.60   $195.60  
  Purchase #2 $194.65   8.500%   $211.1953   $211.20   $211.20   $211.20  
  Purchase #3 $47.36   7.544%   $50.9328   $50.93   $50.95   $50.90  
  Purchase #4 $240.62   8.717%   $261.5948   $261.59   $261.60   $261.60  
  Purchase #5 $124.56   4.694%   $130.4068   $130.41   $130.40   $130.40  
  Purchase #6 $167.65   5.863%   $177.4793   $177.48   $177.50   $177.50  
  Purchase #7 $5.29   3.522%   $5.4763   $5.48   $5.50   $5.50  
  7 purchase totals = $953.70       $1,032.6970   $1,032.70   $1,032.75   $1,032.70