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 $88.46   4.722%   $92.6371   $92.64   $92.65   $92.60  
  Purchase #2 $165.74   9.490%   $181.4687   $181.47   $181.45   $181.50  
  Purchase #3 $159.97   3.396%   $165.4026   $165.40   $165.40   $165.40  
  Purchase #4 $246.36   11.448%   $274.5633   $274.56   $274.55   $274.60  
  Purchase #5 $114.55   9.581%   $125.525   $125.53   $125.55   $125.50  
  Purchase #6 $236.95   4.626%   $247.9113   $247.91   $247.90   $247.90  
  Purchase #7 $107.51   10.616%   $118.9233   $118.92   $118.90   $118.90  
  7 purchase totals = $1,119.54       $1,206.4313   $1,206.43   $1,206.40   $1,206.40