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 $196.37   6.392%   $208.922   $208.92   $208.90   $208.90  
  Purchase #2 $204.87   11.540%   $228.512   $228.51   $228.50   $228.50  
  Purchase #3 $47.65   8.663%   $51.7779   $51.78   $51.80   $51.80  
  Purchase #4 $180.80   6.806%   $193.1052   $193.11   $193.10   $193.10  
  Purchase #5 $184.85   5.497%   $195.0112   $195.01   $195.00   $195.00  
  Purchase #6 $62.27   9.672%   $68.2928   $68.29   $68.30   $68.30  
  Purchase #7 $95.95   5.533%   $101.2589   $101.26   $101.25   $101.30  
  7 purchase totals = $972.76       $1,046.8800   $1,046.88   $1,046.85   $1,046.90