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 $214.43   13.610%   $243.6139   $243.61   $243.60   $243.60  
  Purchase #2 $200.74   3.148%   $207.0593   $207.06   $207.05   $207.10  
  Purchase #3 $179.95   8.496%   $195.2386   $195.24   $195.25   $195.20  
  Purchase #4 $166.59   5.808%   $176.2655   $176.27   $176.25   $176.30  
  Purchase #5 $223.29   6.825%   $238.5295   $238.53   $238.55   $238.50  
  Purchase #6 $111.61   5.177%   $117.388   $117.39   $117.40   $117.40  
  Purchase #7 $250.96   5.215%   $264.0476   $264.05   $264.05   $264.00  
  7 purchase totals = $1,347.57       $1,442.1424   $1,442.15   $1,442.15   $1,442.10