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 $164.76   10.418%   $181.9247   $181.92   $181.90   $181.90  
  Purchase #2 $213.79   9.828%   $234.8013   $234.80   $234.80   $234.80  
  Purchase #3 $224.39   4.267%   $233.9647   $233.96   $233.95   $234.00  
  Purchase #4 $59.62   4.645%   $62.3893   $62.39   $62.40   $62.40  
  Purchase #5 $223.62   6.198%   $237.48   $237.48   $237.50   $237.50  
  Purchase #6 $235.41   7.545%   $253.1717   $253.17   $253.15   $253.20  
  Purchase #7 $9.64   12.765%   $10.8705   $10.87   $10.85   $10.90  
  7 purchase totals = $1,131.23       $1,214.6022   $1,214.59   $1,214.55   $1,214.70