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 $244.62   9.230%   $267.1984   $267.20   $267.20   $267.20  
  Purchase #2 $56.77   10.704%   $62.8467   $62.85   $62.85   $62.80  
  Purchase #3 $111.52   5.367%   $117.5053   $117.51   $117.50   $117.50  
  Purchase #4 $193.34   9.786%   $212.2603   $212.26   $212.25   $212.30  
  Purchase #5 $213.37   4.545%   $223.0677   $223.07   $223.05   $223.10  
  Purchase #6 $26.26   7.836%   $28.3177   $28.32   $28.30   $28.30  
  Purchase #7 $248.85   7.747%   $268.1284   $268.13   $268.15   $268.10  
  7 purchase totals = $1,094.73       $1,179.3245   $1,179.34   $1,179.30   $1,179.30