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 $229.72   3.183%   $237.032   $237.03   $237.05   $237.00  
  Purchase #2 $118.82   7.416%   $127.6317   $127.63   $127.65   $127.60  
  Purchase #3 $242.87   3.267%   $250.8046   $250.80   $250.80   $250.80  
  Purchase #4 $177.48   3.429%   $183.5658   $183.57   $183.55   $183.60  
  Purchase #5 $119.72   11.690%   $133.7153   $133.72   $133.70   $133.70  
  Purchase #6 $96.83   9.486%   $106.0153   $106.02   $106.00   $106.00  
  Purchase #7 $146.88   6.167%   $155.9381   $155.94   $155.95   $155.90  
  7 purchase totals = $1,132.32       $1,194.7028   $1,194.71   $1,194.70   $1,194.60