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 $155.77   11.832%   $174.2007   $174.20   $174.20   $174.20  
  Purchase #2 $122.57   4.151%   $127.6579   $127.66   $127.65   $127.70  
  Purchase #3 $35.81   7.488%   $38.4915   $38.49   $38.50   $38.50  
  Purchase #4 $83.47   5.164%   $87.7804   $87.78   $87.80   $87.80  
  Purchase #5 $96.28   6.145%   $102.1964   $102.20   $102.20   $102.20  
  Purchase #6 $57.95   5.502%   $61.1384   $61.14   $61.15   $61.10  
  Purchase #7 $151.27   6.135%   $160.5504   $160.55   $160.55   $160.60  
  7 purchase totals = $703.12       $752.0157   $752.02   $752.05   $752.10