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 $246.38   6.401%   $262.1508   $262.15   $262.15   $262.20  
  Purchase #2 $21.96   9.613%   $24.071   $24.07   $24.05   $24.10  
  Purchase #3 $242.44   13.742%   $275.7561   $275.76   $275.75   $275.80  
  Purchase #4 $153.37   6.718%   $163.6734   $163.67   $163.65   $163.70  
  Purchase #5 $42.93   6.585%   $45.7569   $45.76   $45.75   $45.80  
  Purchase #6 $163.28   9.782%   $179.252   $179.25   $179.25   $179.30  
  Purchase #7 $142.99   5.468%   $150.8087   $150.81   $150.80   $150.80  
  7 purchase totals = $1,013.35       $1,101.4689   $1,101.47   $1,101.40   $1,101.70