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 $81.95   4.463%   $85.6074   $85.61   $85.60   $85.60  
  Purchase #2 $13.75   5.787%   $14.5457   $14.55   $14.55   $14.50  
  Purchase #3 $55.59   11.797%   $62.148   $62.15   $62.15   $62.10  
  Purchase #4 $77.89   7.582%   $83.7956   $83.80   $83.80   $83.80  
  Purchase #5 $176.36   12.783%   $198.9041   $198.90   $198.90   $198.90  
  Purchase #6 $221.49   12.272%   $248.6713   $248.67   $248.65   $248.70  
  Purchase #7 $212.80   8.721%   $231.3583   $231.36   $231.35   $231.40  
  7 purchase totals = $839.83       $925.0304   $925.04   $925.00   $925.00