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 $205.28   10.591%   $227.0212   $227.02   $227.00   $227.00  
  Purchase #2 $49.30   10.198%   $54.3276   $54.33   $54.35   $54.30  
  Purchase #3 $105.97   7.560%   $113.9813   $113.98   $114.00   $114.00  
  Purchase #4 $160.98   6.509%   $171.4582   $171.46   $171.45   $171.50  
  Purchase #5 $238.39   8.658%   $259.0298   $259.03   $259.05   $259.00  
  Purchase #6 $107.51   5.531%   $113.4564   $113.46   $113.45   $113.50  
  Purchase #7 $105.87   8.314%   $114.672   $114.67   $114.65   $114.70  
  7 purchase totals = $973.30       $1,053.9465   $1,053.95   $1,053.95   $1,054.00