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 $43.27   6.797%   $46.2111   $46.21   $46.20   $46.20  
  Purchase #2 $228.38   5.791%   $241.6055   $241.61   $241.60   $241.60  
  Purchase #3 $50.92   10.823%   $56.4311   $56.43   $56.45   $56.40  
  Purchase #4 $81.25   5.205%   $85.4791   $85.48   $85.50   $85.50  
  Purchase #5 $120.71   13.174%   $136.6123   $136.61   $136.60   $136.60  
  Purchase #6 $132.54   7.103%   $141.9543   $141.95   $141.95   $142.00  
  Purchase #7 $144.36   6.458%   $153.6828   $153.68   $153.70   $153.70  
  7 purchase totals = $801.43       $861.9762   $861.97   $862.00   $862.00