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 $153.87   13.709%   $174.964   $174.96   $174.95   $175.00  
  Purchase #2 $185.64   5.572%   $195.9839   $195.98   $196.00   $196.00  
  Purchase #3 $78.99   9.292%   $86.3298   $86.33   $86.35   $86.30  
  Purchase #4 $241.96   10.264%   $266.7948   $266.79   $266.80   $266.80  
  Purchase #5 $199.35   12.608%   $224.484   $224.48   $224.50   $224.50  
  Purchase #6 $19.27   10.820%   $21.355   $21.36   $21.35   $21.40  
  Purchase #7 $239.75   11.157%   $266.4989   $266.50   $266.50   $266.50  
  7 purchase totals = $1,118.83       $1,236.4104   $1,236.40   $1,236.45   $1,236.50