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 $196.35   5.583%   $207.3122   $207.31   $207.30   $207.30  
  Purchase #2 $158.52   8.547%   $172.0687   $172.07   $172.05   $172.10  
  Purchase #3 $64.97   3.863%   $67.4798   $67.48   $67.50   $67.50  
  Purchase #4 $151.44   5.715%   $160.0948   $160.09   $160.10   $160.10  
  Purchase #5 $219.96   4.429%   $229.702   $229.70   $229.70   $229.70  
  Purchase #6 $168.36   4.661%   $176.2073   $176.21   $176.20   $176.20  
  Purchase #7 $31.31   7.767%   $33.7418   $33.74   $33.75   $33.70  
  7 purchase totals = $990.91       $1,046.6066   $1,046.60   $1,046.60   $1,046.60