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 $86.77   9.804%   $95.2769   $95.28   $95.30   $95.30  
  Purchase #2 $174.67   10.232%   $192.5422   $192.54   $192.55   $192.50  
  Purchase #3 $237.98   12.418%   $267.5324   $267.53   $267.55   $267.50  
  Purchase #4 $165.49   13.164%   $187.2751   $187.28   $187.30   $187.30  
  Purchase #5 $113.91   3.835%   $118.2784   $118.28   $118.30   $118.30  
  Purchase #6 $81.90   3.773%   $84.9901   $84.99   $85.00   $85.00  
  Purchase #7 $163.27   12.362%   $183.4534   $183.45   $183.45   $183.50  
  7 purchase totals = $1,023.99       $1,129.3485   $1,129.35   $1,129.45   $1,129.40