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 $243.70   7.518%   $262.0214   $262.02   $262.00   $262.00  
  Purchase #2 $248.33   4.304%   $259.0181   $259.02   $259.00   $259.00  
  Purchase #3 $45.37   4.236%   $47.2919   $47.29   $47.30   $47.30  
  Purchase #4 $164.53   6.528%   $175.2705   $175.27   $175.25   $175.30  
  Purchase #5 $124.45   8.486%   $135.0108   $135.01   $135.00   $135.00  
  Purchase #6 $81.43   6.374%   $86.6203   $86.62   $86.60   $86.60  
  Purchase #7 $117.79   7.212%   $126.285   $126.29   $126.30   $126.30  
  7 purchase totals = $1,025.60       $1,091.5180   $1,091.52   $1,091.45   $1,091.50