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 $96.38   9.614%   $105.646   $105.65   $105.65   $105.60  
  Purchase #2 $60.55   9.471%   $66.2847   $66.28   $66.30   $66.30  
  Purchase #3 $71.36   13.365%   $80.8973   $80.90   $80.90   $80.90  
  Purchase #4 $176.71   8.382%   $191.5218   $191.52   $191.50   $191.50  
  Purchase #5 $145.97   8.653%   $158.6008   $158.60   $158.60   $158.60  
  Purchase #6 $189.52   10.633%   $209.6717   $209.67   $209.65   $209.70  
  Purchase #7 $66.93   4.259%   $69.7805   $69.78   $69.80   $69.80  
  7 purchase totals = $807.42       $882.4028   $882.40   $882.40   $882.40