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 $146.88   5.331%   $154.7102   $154.71   $154.70   $154.70  
  Purchase #2 $176.82   12.344%   $198.6467   $198.65   $198.65   $198.60  
  Purchase #3 $213.43   7.503%   $229.4437   $229.44   $229.45   $229.40  
  Purchase #4 $86.71   5.557%   $91.5285   $91.53   $91.55   $91.50  
  Purchase #5 $101.91   6.384%   $108.4159   $108.42   $108.40   $108.40  
  Purchase #6 $201.82   5.803%   $213.5316   $213.53   $213.55   $213.50  
  Purchase #7 $171.87   8.144%   $185.8671   $185.87   $185.85   $185.90  
  7 purchase totals = $1,099.44       $1,182.1437   $1,182.15   $1,182.15   $1,182.00