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 $88.55   8.366%   $95.9581   $95.96   $95.95   $96.00  
  Purchase #2 $68.25   13.327%   $77.3457   $77.35   $77.35   $77.30  
  Purchase #3 $165.35   3.453%   $171.0595   $171.06   $171.05   $171.10  
  Purchase #4 $8.39   13.310%   $9.5067   $9.51   $9.50   $9.50  
  Purchase #5 $153.33   9.309%   $167.6035   $167.60   $167.60   $167.60  
  Purchase #6 $152.63   8.217%   $165.1716   $165.17   $165.15   $165.20  
  Purchase #7 $240.69   10.548%   $266.078   $266.08   $266.10   $266.10  
  7 purchase totals = $877.19       $952.7231   $952.73   $952.70   $952.80