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 $67.27   13.864%   $76.5963   $76.60   $76.60   $76.60  
  Purchase #2 $187.28   7.865%   $202.0096   $202.01   $202.00   $202.00  
  Purchase #3 $241.81   7.154%   $259.1091   $259.11   $259.10   $259.10  
  Purchase #4 $16.37   13.649%   $18.6043   $18.60   $18.60   $18.60  
  Purchase #5 $60.91   3.490%   $63.0358   $63.04   $63.05   $63.00  
  Purchase #6 $221.40   3.776%   $229.7601   $229.76   $229.75   $229.80  
  Purchase #7 $166.66   12.401%   $187.3275   $187.33   $187.35   $187.30  
  7 purchase totals = $961.70       $1,036.4427   $1,036.45   $1,036.45   $1,036.40