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 $85.56   11.299%   $95.2274   $95.23   $95.25   $95.20  
  Purchase #2 $171.68   7.585%   $184.7019   $184.70   $184.70   $184.70  
  Purchase #3 $107.54   3.781%   $111.6061   $111.61   $111.60   $111.60  
  Purchase #4 $157.54   8.186%   $170.4362   $170.44   $170.45   $170.40  
  Purchase #5 $204.97   9.451%   $224.3417   $224.34   $224.35   $224.30  
  Purchase #6 $193.68   6.495%   $206.2595   $206.26   $206.25   $206.30  
  Purchase #7 $223.78   13.243%   $253.4152   $253.42   $253.40   $253.40  
  7 purchase totals = $1,144.75       $1,245.9880   $1,246.00   $1,246.00   $1,245.90