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 $183.48   5.823%   $194.164   $194.16   $194.15   $194.20  
  Purchase #2 $156.66   6.553%   $166.9259   $166.93   $166.95   $166.90  
  Purchase #3 $164.69   10.189%   $181.4703   $181.47   $181.45   $181.50  
  Purchase #4 $235.60   4.537%   $246.2892   $246.29   $246.30   $246.30  
  Purchase #5 $45.74   3.789%   $47.4731   $47.47   $47.45   $47.50  
  Purchase #6 $98.71   8.241%   $106.8447   $106.84   $106.85   $106.80  
  Purchase #7 $110.49   13.744%   $125.6757   $125.68   $125.70   $125.70  
  7 purchase totals = $995.37       $1,068.8429   $1,068.84   $1,068.85   $1,068.90