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 $58.39   8.310%   $63.2422   $63.24   $63.25   $63.20  
  Purchase #2 $176.59   4.300%   $184.1834   $184.18   $184.20   $184.20  
  Purchase #3 $62.56   9.659%   $68.6027   $68.60   $68.60   $68.60  
  Purchase #4 $181.48   9.864%   $199.3812   $199.38   $199.40   $199.40  
  Purchase #5 $207.84   4.407%   $216.9995   $217.00   $217.00   $217.00  
  Purchase #6 $11.83   7.777%   $12.75   $12.75   $12.75   $12.80  
  Purchase #7 $192.62   8.163%   $208.3436   $208.34   $208.35   $208.30  
  7 purchase totals = $891.31       $953.5026   $953.49   $953.55   $953.50