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 $164.77   5.705%   $174.1701   $174.17   $174.15   $174.20  
  Purchase #2 $104.96   9.546%   $114.9795   $114.98   $115.00   $115.00  
  Purchase #3 $89.59   5.873%   $94.8516   $94.85   $94.85   $94.90  
  Purchase #4 $203.52   5.395%   $214.4999   $214.50   $214.50   $214.50  
  Purchase #5 $249.83   13.776%   $284.2466   $284.25   $284.25   $284.20  
  Purchase #6 $95.74   7.697%   $103.1091   $103.11   $103.10   $103.10  
  Purchase #7 $201.46   8.629%   $218.844   $218.84   $218.85   $218.80  
  7 purchase totals = $1,109.87       $1,204.7008   $1,204.70   $1,204.70   $1,204.70