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 $167.94   8.767%   $182.6633   $182.66   $182.65   $182.70  
  Purchase #2 $214.86   9.447%   $235.1578   $235.16   $235.15   $235.20  
  Purchase #3 $87.70   11.488%   $97.775   $97.78   $97.80   $97.80  
  Purchase #4 $66.90   4.316%   $69.7874   $69.79   $69.80   $69.80  
  Purchase #5 $141.89   8.194%   $153.5165   $153.52   $153.50   $153.50  
  Purchase #6 $43.95   3.505%   $45.4904   $45.49   $45.50   $45.50  
  Purchase #7 $174.74   4.305%   $182.2626   $182.26   $182.25   $182.30  
  7 purchase totals = $897.98       $966.6530   $966.66   $966.65   $966.80