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 $119.58   5.326%   $125.9488   $125.95   $125.95   $125.90  
  Purchase #2 $189.96   13.441%   $215.4925   $215.49   $215.50   $215.50  
  Purchase #3 $60.87   3.490%   $62.9944   $62.99   $63.00   $63.00  
  Purchase #4 $95.47   11.405%   $106.3584   $106.36   $106.35   $106.40  
  Purchase #5 $184.47   9.439%   $201.8821   $201.88   $201.90   $201.90  
  Purchase #6 $243.39   9.656%   $266.8917   $266.89   $266.90   $266.90  
  Purchase #7 $65.36   10.519%   $72.2352   $72.24   $72.25   $72.20  
  7 purchase totals = $959.10       $1,051.8031   $1,051.80   $1,051.85   $1,051.80