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 $66.77   7.826%   $71.9954   $72.00   $72.00   $72.00  
  Purchase #2 $134.82   13.374%   $152.8508   $152.85   $152.85   $152.90  
  Purchase #3 $200.99   5.646%   $212.3379   $212.34   $212.35   $212.30  
  Purchase #4 $118.67   12.828%   $133.893   $133.89   $133.90   $133.90  
  Purchase #5 $192.44   11.433%   $214.4417   $214.44   $214.45   $214.40  
  Purchase #6 $196.60   8.677%   $213.659   $213.66   $213.65   $213.70  
  Purchase #7 $6.90   4.818%   $7.2324   $7.23   $7.25   $7.20  
  7 purchase totals = $917.19       $1,006.4102   $1,006.41   $1,006.45   $1,006.40