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 $41.71   4.406%   $43.5477   $43.55   $43.55   $43.50  
  Purchase #2 $220.86   9.465%   $241.7644   $241.76   $241.75   $241.80  
  Purchase #3 $95.79   7.708%   $103.1735   $103.17   $103.15   $103.20  
  Purchase #4 $221.58   6.187%   $235.2892   $235.29   $235.30   $235.30  
  Purchase #5 $30.45   10.551%   $33.6628   $33.66   $33.65   $33.70  
  Purchase #6 $207.96   9.629%   $227.9845   $227.98   $228.00   $228.00  
  Purchase #7 $108.78   5.510%   $114.7738   $114.77   $114.75   $114.80  
  7 purchase totals = $927.13       $1,000.1959   $1,000.18   $1,000.15   $1,000.30