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 $184.41   7.689%   $198.5893   $198.59   $198.60   $198.60  
  Purchase #2 $114.78   4.501%   $119.9462   $119.95   $119.95   $119.90  
  Purchase #3 $76.52   8.844%   $83.2874   $83.29   $83.30   $83.30  
  Purchase #4 $98.31   4.723%   $102.9532   $102.95   $102.95   $103.00  
  Purchase #5 $163.59   4.124%   $170.3365   $170.34   $170.35   $170.30  
  Purchase #6 $29.41   11.328%   $32.7416   $32.74   $32.75   $32.70  
  Purchase #7 $161.80   7.809%   $174.435   $174.44   $174.45   $174.40  
  7 purchase totals = $828.82       $882.2892   $882.30   $882.35   $882.20