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 $182.57   7.382%   $196.0473   $196.05   $196.05   $196.00  
  Purchase #2 $206.36   5.334%   $217.3672   $217.37   $217.35   $217.40  
  Purchase #3 $221.77   5.197%   $233.2954   $233.30   $233.30   $233.30  
  Purchase #4 $239.57   7.291%   $257.037   $257.04   $257.05   $257.00  
  Purchase #5 $103.39   4.820%   $108.3734   $108.37   $108.35   $108.40  
  Purchase #6 $29.95   7.400%   $32.1663   $32.17   $32.15   $32.20  
  Purchase #7 $31.96   4.153%   $33.2873   $33.29   $33.30   $33.30  
  7 purchase totals = $1,015.57       $1,077.5739   $1,077.59   $1,077.55   $1,077.60