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 $59.39   3.301%   $61.3505   $61.35   $61.35   $61.40  
  Purchase #2 $116.57   11.573%   $130.0606   $130.06   $130.05   $130.10  
  Purchase #3 $130.35   9.199%   $142.3409   $142.34   $142.35   $142.30  
  Purchase #4 $182.66   10.188%   $201.2694   $201.27   $201.25   $201.30  
  Purchase #5 $241.53   4.478%   $252.3457   $252.35   $252.35   $252.30  
  Purchase #6 $175.54   9.128%   $191.5633   $191.56   $191.55   $191.60  
  Purchase #7 $223.85   10.714%   $247.8333   $247.83   $247.85   $247.80  
  7 purchase totals = $1,129.89       $1,226.7637   $1,226.76   $1,226.75   $1,226.80