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 $67.92   11.800%   $75.9346   $75.93   $75.95   $75.90  
  Purchase #2 $161.65   9.683%   $177.3026   $177.30   $177.30   $177.30  
  Purchase #3 $117.62   7.550%   $126.5003   $126.50   $126.50   $126.50  
  Purchase #4 $195.42   5.407%   $205.9864   $205.99   $206.00   $206.00  
  Purchase #5 $142.86   5.567%   $150.813   $150.81   $150.80   $150.80  
  Purchase #6 $242.34   12.272%   $272.08   $272.08   $272.10   $272.10  
  Purchase #7 $127.94   10.561%   $141.4517   $141.45   $141.45   $141.50  
  7 purchase totals = $1,055.75       $1,150.0686   $1,150.06   $1,150.10   $1,150.10