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 $56.87   8.296%   $61.5879   $61.59   $61.60   $61.60  
  Purchase #2 $193.57   6.500%   $206.1521   $206.15   $206.15   $206.20  
  Purchase #3 $220.74   5.770%   $233.4767   $233.48   $233.50   $233.50  
  Purchase #4 $73.86   11.297%   $82.204   $82.20   $82.20   $82.20  
  Purchase #5 $158.99   8.708%   $172.8348   $172.83   $172.85   $172.80  
  Purchase #6 $229.86   9.387%   $251.437   $251.44   $251.45   $251.40  
  Purchase #7 $23.66   4.140%   $24.6395   $24.64   $24.65   $24.60  
  7 purchase totals = $957.55       $1,032.3320   $1,032.33   $1,032.40   $1,032.30