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 $174.29   5.571%   $183.9997   $184.00   $184.00   $184.00  
  Purchase #2 $114.87   7.335%   $123.2957   $123.30   $123.30   $123.30  
  Purchase #3 $95.82   11.320%   $106.6668   $106.67   $106.65   $106.70  
  Purchase #4 $233.41   12.109%   $261.6736   $261.67   $261.65   $261.70  
  Purchase #5 $22.75   4.363%   $23.7426   $23.74   $23.75   $23.70  
  Purchase #6 $15.48   11.549%   $17.2678   $17.27   $17.25   $17.30  
  Purchase #7 $15.33   4.294%   $15.9883   $15.99   $16.00   $16.00  
  7 purchase totals = $671.95       $732.6345   $732.64   $732.60   $732.70