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 $211.41   11.485%   $235.6904   $235.69   $235.70   $235.70  
  Purchase #2 $33.43   5.801%   $35.3693   $35.37   $35.35   $35.40  
  Purchase #3 $188.77   12.181%   $211.7641   $211.76   $211.75   $211.80  
  Purchase #4 $154.91   11.406%   $172.579   $172.58   $172.60   $172.60  
  Purchase #5 $244.77   5.394%   $257.9729   $257.97   $257.95   $258.00  
  Purchase #6 $106.36   3.663%   $110.256   $110.26   $110.25   $110.30  
  Purchase #7 $30.91   4.514%   $32.3053   $32.31   $32.30   $32.30  
  7 purchase totals = $970.56       $1,055.9370   $1,055.94   $1,055.90   $1,056.10