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 $171.33   9.107%   $186.933   $186.93   $186.95   $186.90  
  Purchase #2 $209.45   7.107%   $224.3356   $224.34   $224.35   $224.30  
  Purchase #3 $111.32   6.296%   $118.3287   $118.33   $118.35   $118.30  
  Purchase #4 $195.41   10.223%   $215.3868   $215.39   $215.40   $215.40  
  Purchase #5 $230.87   4.803%   $241.9587   $241.96   $241.95   $242.00  
  Purchase #6 $129.56   13.775%   $147.4069   $147.41   $147.40   $147.40  
  Purchase #7 $182.77   8.423%   $198.1647   $198.16   $198.15   $198.20  
  7 purchase totals = $1,230.71       $1,332.5144   $1,332.52   $1,332.55   $1,332.50