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 $237.28   10.740%   $262.7639   $262.76   $262.75   $262.80  
  Purchase #2 $215.39   7.852%   $232.3024   $232.30   $232.30   $232.30  
  Purchase #3 $113.42   5.179%   $119.294   $119.29   $119.30   $119.30  
  Purchase #4 $213.34   11.311%   $237.4709   $237.47   $237.45   $237.50  
  Purchase #5 $52.58   9.468%   $57.5583   $57.56   $57.55   $57.60  
  Purchase #6 $144.87   6.437%   $154.1953   $154.20   $154.20   $154.20  
  Purchase #7 $152.34   10.540%   $168.3966   $168.40   $168.40   $168.40  
  7 purchase totals = $1,129.22       $1,231.9814   $1,231.98   $1,231.95   $1,232.10