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 $226.81   5.241%   $238.6971   $238.70   $238.70   $238.70  
  Purchase #2 $190.62   7.722%   $205.3397   $205.34   $205.35   $205.30  
  Purchase #3 $48.49   7.185%   $51.974   $51.97   $51.95   $52.00  
  Purchase #4 $222.25   7.233%   $238.3253   $238.33   $238.35   $238.30  
  Purchase #5 $137.61   8.726%   $149.6178   $149.62   $149.60   $149.60  
  Purchase #6 $184.29   11.501%   $205.4852   $205.49   $205.50   $205.50  
  Purchase #7 $227.33   7.604%   $244.6162   $244.62   $244.60   $244.60  
  7 purchase totals = $1,237.40       $1,334.0553   $1,334.07   $1,334.05   $1,334.00