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 $176.89   8.528%   $191.9752   $191.98   $192.00   $192.00  
  Purchase #2 $103.62   12.107%   $116.1653   $116.17   $116.15   $116.20  
  Purchase #3 $56.63   10.765%   $62.7262   $62.73   $62.75   $62.70  
  Purchase #4 $173.68   3.227%   $179.2847   $179.28   $179.30   $179.30  
  Purchase #5 $98.51   9.321%   $107.6921   $107.69   $107.70   $107.70  
  Purchase #6 $54.30   13.110%   $61.4187   $61.42   $61.40   $61.40  
  Purchase #7 $193.69   9.742%   $212.5593   $212.56   $212.55   $212.60  
  7 purchase totals = $857.32       $931.8215   $931.83   $931.85   $931.90