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 $59.82   13.513%   $67.9035   $67.90   $67.90   $67.90  
  Purchase #2 $207.29   10.706%   $229.4825   $229.48   $229.50   $229.50  
  Purchase #3 $167.37   4.254%   $174.4899   $174.49   $174.50   $174.50  
  Purchase #4 $226.34   13.766%   $257.498   $257.50   $257.50   $257.50  
  Purchase #5 $201.37   9.265%   $220.0269   $220.03   $220.05   $220.00  
  Purchase #6 $188.33   3.522%   $194.963   $194.96   $194.95   $195.00  
  Purchase #7 $175.68   13.322%   $199.0841   $199.08   $199.10   $199.10  
  7 purchase totals = $1,226.20       $1,343.4479   $1,343.44   $1,343.50   $1,343.50