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 $194.98   3.120%   $201.0634   $201.06   $201.05   $201.10  
  Purchase #2 $232.89   6.425%   $247.8532   $247.85   $247.85   $247.90  
  Purchase #3 $185.68   5.407%   $195.7197   $195.72   $195.70   $195.70  
  Purchase #4 $85.58   4.188%   $89.1641   $89.16   $89.15   $89.20  
  Purchase #5 $134.59   13.388%   $152.6089   $152.61   $152.60   $152.60  
  Purchase #6 $217.48   8.346%   $235.6309   $235.63   $235.65   $235.60  
  Purchase #7 $62.31   12.425%   $70.052   $70.05   $70.05   $70.10  
  7 purchase totals = $1,113.51       $1,192.0922   $1,192.08   $1,192.05   $1,192.20