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 $166.90   5.444%   $175.986   $175.99   $176.00   $176.00  
  Purchase #2 $138.47   3.205%   $142.908   $142.91   $142.90   $142.90  
  Purchase #3 $30.73   3.806%   $31.8996   $31.90   $31.90   $31.90  
  Purchase #4 $124.90   4.225%   $130.177   $130.18   $130.20   $130.20  
  Purchase #5 $9.78   4.296%   $10.2001   $10.20   $10.20   $10.20  
  Purchase #6 $187.37   5.574%   $197.814   $197.81   $197.80   $197.80  
  Purchase #7 $219.36   10.771%   $242.9873   $242.99   $243.00   $243.00  
  7 purchase totals = $877.51       $931.9720   $931.98   $932.00   $932.00