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 $95.29   11.204%   $105.9663   $105.97   $105.95   $106.00  
  Purchase #2 $197.53   8.599%   $214.5156   $214.52   $214.50   $214.50  
  Purchase #3 $142.75   12.430%   $160.4938   $160.49   $160.50   $160.50  
  Purchase #4 $241.28   7.378%   $259.0816   $259.08   $259.10   $259.10  
  Purchase #5 $76.71   8.177%   $82.9826   $82.98   $83.00   $83.00  
  Purchase #6 $151.74   9.192%   $165.6879   $165.69   $165.70   $165.70  
  Purchase #7 $224.78   5.213%   $236.4978   $236.50   $236.50   $236.50  
  7 purchase totals = $1,130.08       $1,225.2256   $1,225.23   $1,225.25   $1,225.30