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 $195.82   9.679%   $214.7734   $214.77   $214.75   $214.80  
  Purchase #2 $177.45   11.166%   $197.2641   $197.26   $197.25   $197.30  
  Purchase #3 $124.39   11.294%   $138.4386   $138.44   $138.45   $138.40  
  Purchase #4 $27.62   6.217%   $29.3371   $29.34   $29.35   $29.30  
  Purchase #5 $83.60   3.419%   $86.4583   $86.46   $86.45   $86.50  
  Purchase #6 $214.66   10.547%   $237.3002   $237.30   $237.30   $237.30  
  Purchase #7 $106.30   11.676%   $118.7116   $118.71   $118.70   $118.70  
  7 purchase totals = $929.84       $1,022.2833   $1,022.28   $1,022.25   $1,022.30