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 $116.77   5.464%   $123.1503   $123.15   $123.15   $123.20  
  Purchase #2 $182.87   8.531%   $198.4706   $198.47   $198.45   $198.50  
  Purchase #3 $234.57   4.152%   $244.3093   $244.31   $244.30   $244.30  
  Purchase #4 $220.51   5.711%   $233.1033   $233.10   $233.10   $233.10  
  Purchase #5 $164.69   5.206%   $173.2638   $173.26   $173.25   $173.30  
  Purchase #6 $111.98   10.756%   $124.0246   $124.02   $124.00   $124.00  
  Purchase #7 $232.95   7.375%   $250.1301   $250.13   $250.15   $250.10  
  7 purchase totals = $1,264.34       $1,346.4520   $1,346.44   $1,346.40   $1,346.50