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 $88.37   4.672%   $92.4986   $92.50   $92.50   $92.50  
  Purchase #2 $196.99   11.438%   $219.5217   $219.52   $219.50   $219.50  
  Purchase #3 $46.55   11.472%   $51.8902   $51.89   $51.90   $51.90  
  Purchase #4 $213.26   6.380%   $226.866   $226.87   $226.85   $226.90  
  Purchase #5 $149.45   5.455%   $157.6025   $157.60   $157.60   $157.60  
  Purchase #6 $213.84   7.831%   $230.5858   $230.59   $230.60   $230.60  
  Purchase #7 $168.28   8.319%   $182.2792   $182.28   $182.30   $182.30  
  7 purchase totals = $1,076.74       $1,161.2440   $1,161.25   $1,161.25   $1,161.30