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 $241.34   7.742%   $260.0245   $260.02   $260.00   $260.00  
  Purchase #2 $142.36   6.580%   $151.7273   $151.73   $151.75   $151.70  
  Purchase #3 $212.70   13.460%   $241.3294   $241.33   $241.35   $241.30  
  Purchase #4 $39.33   10.232%   $43.3542   $43.35   $43.35   $43.40  
  Purchase #5 $119.74   11.718%   $133.7711   $133.77   $133.75   $133.80  
  Purchase #6 $109.82   11.792%   $122.77   $122.77   $122.75   $122.80  
  Purchase #7 $140.68   12.808%   $158.6983   $158.70   $158.70   $158.70  
  7 purchase totals = $1,005.97       $1,111.6748   $1,111.67   $1,111.65   $1,111.70