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 $118.78   5.233%   $124.9958   $125.00   $125.00   $125.00  
  Purchase #2 $233.45   11.795%   $260.9854   $260.99   $261.00   $261.00  
  Purchase #3 $152.60   7.634%   $164.2495   $164.25   $164.25   $164.20  
  Purchase #4 $218.25   6.402%   $232.2224   $232.22   $232.20   $232.20  
  Purchase #5 $147.77   4.689%   $154.6989   $154.70   $154.70   $154.70  
  Purchase #6 $231.73   3.634%   $240.1511   $240.15   $240.15   $240.20  
  Purchase #7 $234.30   4.172%   $244.075   $244.08   $244.10   $244.10  
  7 purchase totals = $1,336.88       $1,421.3781   $1,421.39   $1,421.40   $1,421.40