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 $91.97   4.116%   $95.7555   $95.76   $95.75   $95.80  
  Purchase #2 $209.51   8.159%   $226.6039   $226.60   $226.60   $226.60  
  Purchase #3 $141.79   8.485%   $153.8209   $153.82   $153.80   $153.80  
  Purchase #4 $236.60   5.538%   $249.7029   $249.70   $249.70   $249.70  
  Purchase #5 $106.88   10.438%   $118.0361   $118.04   $118.05   $118.00  
  Purchase #6 $14.69   8.404%   $15.9245   $15.92   $15.90   $15.90  
  Purchase #7 $73.92   4.662%   $77.3662   $77.37   $77.35   $77.40  
  7 purchase totals = $875.36       $937.2100   $937.21   $937.15   $937.20