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 $174.70   11.440%   $194.6857   $194.69   $194.70   $194.70  
  Purchase #2 $71.80   3.276%   $74.1522   $74.15   $74.15   $74.20  
  Purchase #3 $158.55   11.468%   $176.7325   $176.73   $176.75   $176.70  
  Purchase #4 $133.64   5.755%   $141.331   $141.33   $141.35   $141.30  
  Purchase #5 $121.80   12.451%   $136.9653   $136.97   $136.95   $137.00  
  Purchase #6 $10.40   6.751%   $11.1021   $11.10   $11.10   $11.10  
  Purchase #7 $111.77   11.420%   $124.5341   $124.53   $124.55   $124.50  
  7 purchase totals = $782.66       $859.5029   $859.50   $859.55   $859.50