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 $179.72   13.856%   $204.622   $204.62   $204.60   $204.60  
  Purchase #2 $215.56   7.801%   $232.3758   $232.38   $232.40   $232.40  
  Purchase #3 $234.63   9.539%   $257.0114   $257.01   $257.00   $257.00  
  Purchase #4 $160.95   9.125%   $175.6367   $175.64   $175.65   $175.60  
  Purchase #5 $95.77   12.588%   $107.8255   $107.83   $107.85   $107.80  
  Purchase #6 $165.27   3.113%   $170.4149   $170.41   $170.40   $170.40  
  Purchase #7 $134.28   9.718%   $147.3293   $147.33   $147.35   $147.30  
  7 purchase totals = $1,186.18       $1,295.2156   $1,295.22   $1,295.25   $1,295.10