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 $61.51   3.568%   $63.7047   $63.70   $63.70   $63.70  
  Purchase #2 $158.41   6.253%   $168.3154   $168.32   $168.30   $168.30  
  Purchase #3 $143.76   13.855%   $163.6779   $163.68   $163.70   $163.70  
  Purchase #4 $205.39   4.471%   $214.573   $214.57   $214.55   $214.60  
  Purchase #5 $147.72   4.471%   $154.3246   $154.32   $154.30   $154.30  
  Purchase #6 $133.31   10.760%   $147.6542   $147.65   $147.65   $147.70  
  Purchase #7 $122.52   3.283%   $126.5423   $126.54   $126.55   $126.50  
  7 purchase totals = $972.62       $1,038.7921   $1,038.78   $1,038.75   $1,038.80