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 $248.58   6.175%   $263.9298   $263.93   $263.95   $263.90  
  Purchase #2 $223.50   7.514%   $240.2938   $240.29   $240.30   $240.30  
  Purchase #3 $116.41   3.174%   $120.1049   $120.10   $120.10   $120.10  
  Purchase #4 $248.27   11.546%   $276.9353   $276.94   $276.95   $276.90  
  Purchase #5 $134.38   12.497%   $151.1735   $151.17   $151.15   $151.20  
  Purchase #6 $199.84   5.397%   $210.6254   $210.63   $210.65   $210.60  
  Purchase #7 $191.59   5.683%   $202.4781   $202.48   $202.50   $202.50  
  7 purchase totals = $1,362.57       $1,465.5408   $1,465.54   $1,465.60   $1,465.50