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 $66.83   3.244%   $68.998   $69.00   $69.00   $69.00  
  Purchase #2 $141.27   7.591%   $151.9938   $151.99   $152.00   $152.00  
  Purchase #3 $229.37   5.601%   $242.217   $242.22   $242.20   $242.20  
  Purchase #4 $43.82   5.677%   $46.3077   $46.31   $46.30   $46.30  
  Purchase #5 $162.57   11.805%   $181.7614   $181.76   $181.75   $181.80  
  Purchase #6 $188.35   9.264%   $205.7987   $205.80   $205.80   $205.80  
  Purchase #7 $229.97   8.806%   $250.2212   $250.22   $250.20   $250.20  
  7 purchase totals = $1,062.18       $1,147.2978   $1,147.30   $1,147.25   $1,147.30