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 $239.86   8.550%   $260.368   $260.37   $260.35   $260.40  
  Purchase #2 $195.37   8.250%   $211.488   $211.49   $211.50   $211.50  
  Purchase #3 $24.76   4.339%   $25.8343   $25.83   $25.85   $25.80  
  Purchase #4 $141.32   7.195%   $151.488   $151.49   $151.50   $151.50  
  Purchase #5 $160.35   8.160%   $173.4346   $173.43   $173.45   $173.40  
  Purchase #6 $105.88   8.275%   $114.6416   $114.64   $114.65   $114.60  
  Purchase #7 $167.38   11.609%   $186.8111   $186.81   $186.80   $186.80  
  7 purchase totals = $1,034.92       $1,124.0656   $1,124.06   $1,124.10   $1,124.00