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 $62.49   11.659%   $69.7757   $69.78   $69.80   $69.80  
  Purchase #2 $222.94   4.609%   $233.2153   $233.22   $233.20   $233.20  
  Purchase #3 $198.82   8.593%   $215.9046   $215.90   $215.90   $215.90  
  Purchase #4 $126.77   8.162%   $137.117   $137.12   $137.10   $137.10  
  Purchase #5 $193.93   5.218%   $204.0493   $204.05   $204.05   $204.00  
  Purchase #6 $220.85   9.435%   $241.6872   $241.69   $241.70   $241.70  
  Purchase #7 $155.38   5.480%   $163.8948   $163.89   $163.90   $163.90  
  7 purchase totals = $1,181.18       $1,265.6439   $1,265.65   $1,265.65   $1,265.60