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 $247.99   5.762%   $262.2792   $262.28   $262.30   $262.30  
  Purchase #2 $58.35   12.431%   $65.6035   $65.60   $65.60   $65.60  
  Purchase #3 $200.58   11.441%   $223.5284   $223.53   $223.55   $223.50  
  Purchase #4 $107.81   5.106%   $113.3148   $113.31   $113.30   $113.30  
  Purchase #5 $184.31   8.519%   $200.0114   $200.01   $200.00   $200.00  
  Purchase #6 $67.57   12.708%   $76.1568   $76.16   $76.15   $76.20  
  Purchase #7 $154.92   6.848%   $165.5289   $165.53   $165.55   $165.50  
  7 purchase totals = $1,021.53       $1,106.4230   $1,106.42   $1,106.45   $1,106.40