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 $175.58   11.584%   $195.9192   $195.92   $195.90   $195.90  
  Purchase #2 $224.90   11.679%   $251.1661   $251.17   $251.15   $251.20  
  Purchase #3 $185.73   11.193%   $206.5188   $206.52   $206.50   $206.50  
  Purchase #4 $43.87   11.788%   $49.0414   $49.04   $49.05   $49.00  
  Purchase #5 $148.44   5.233%   $156.2079   $156.21   $156.20   $156.20  
  Purchase #6 $238.52   6.572%   $254.1955   $254.20   $254.20   $254.20  
  Purchase #7 $209.95   6.792%   $224.2098   $224.21   $224.20   $224.20  
  7 purchase totals = $1,226.99       $1,337.2587   $1,337.27   $1,337.20   $1,337.20