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 $119.30   6.303%   $126.8195   $126.82   $126.80   $126.80  
  Purchase #2 $199.32   3.126%   $205.5507   $205.55   $205.55   $205.60  
  Purchase #3 $68.81   12.185%   $77.1945   $77.19   $77.20   $77.20  
  Purchase #4 $242.26   13.437%   $274.8125   $274.81   $274.80   $274.80  
  Purchase #5 $193.45   5.567%   $204.2194   $204.22   $204.20   $204.20  
  Purchase #6 $106.83   8.499%   $115.9095   $115.91   $115.90   $115.90  
  Purchase #7 $173.50   10.652%   $191.9812   $191.98   $192.00   $192.00  
  7 purchase totals = $1,103.47       $1,196.4873   $1,196.48   $1,196.45   $1,196.50