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 $216.59   12.767%   $244.242   $244.24   $244.25   $244.20  
  Purchase #2 $93.85   13.308%   $106.3396   $106.34   $106.35   $106.30  
  Purchase #3 $227.88   4.252%   $237.5695   $237.57   $237.55   $237.60  
  Purchase #4 $35.86   9.739%   $39.3524   $39.35   $39.35   $39.40  
  Purchase #5 $77.56   11.677%   $86.6167   $86.62   $86.60   $86.60  
  Purchase #6 $34.54   3.573%   $35.7741   $35.77   $35.75   $35.80  
  Purchase #7 $244.58   6.707%   $260.984   $260.98   $261.00   $261.00  
  7 purchase totals = $930.86       $1,010.8783   $1,010.87   $1,010.85   $1,010.90