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 $164.84   6.791%   $176.0343   $176.03   $176.05   $176.00  
  Purchase #2 $72.61   5.174%   $76.3668   $76.37   $76.35   $76.40  
  Purchase #3 $165.59   6.815%   $176.875   $176.88   $176.90   $176.90  
  Purchase #4 $190.47   11.777%   $212.9017   $212.90   $212.90   $212.90  
  Purchase #5 $99.45   8.205%   $107.6099   $107.61   $107.60   $107.60  
  Purchase #6 $132.85   12.405%   $149.33   $149.33   $149.35   $149.30  
  Purchase #7 $185.86   11.582%   $207.3863   $207.39   $207.40   $207.40  
  7 purchase totals = $1,011.67       $1,106.5040   $1,106.51   $1,106.55   $1,106.50