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 $182.90   13.156%   $206.9623   $206.96   $206.95   $207.00  
  Purchase #2 $96.32   13.395%   $109.2221   $109.22   $109.20   $109.20  
  Purchase #3 $248.63   6.187%   $264.0127   $264.01   $264.00   $264.00  
  Purchase #4 $98.47   12.399%   $110.6793   $110.68   $110.70   $110.70  
  Purchase #5 $209.60   6.377%   $222.9662   $222.97   $222.95   $223.00  
  Purchase #6 $35.58   5.569%   $37.5615   $37.56   $37.55   $37.60  
  Purchase #7 $234.51   5.368%   $247.0985   $247.10   $247.10   $247.10  
  7 purchase totals = $1,106.01       $1,198.5026   $1,198.50   $1,198.45   $1,198.60