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 $94.65   3.824%   $98.2694   $98.27   $98.25   $98.30  
  Purchase #2 $206.68   11.340%   $230.1175   $230.12   $230.10   $230.10  
  Purchase #3 $38.66   13.289%   $43.7975   $43.80   $43.80   $43.80  
  Purchase #4 $171.30   5.774%   $181.1909   $181.19   $181.20   $181.20  
  Purchase #5 $231.76   5.675%   $244.9124   $244.91   $244.90   $244.90  
  Purchase #6 $136.63   4.824%   $143.221   $143.22   $143.20   $143.20  
  Purchase #7 $208.97   9.498%   $228.818   $228.82   $228.80   $228.80  
  7 purchase totals = $1,088.65       $1,170.3267   $1,170.33   $1,170.25   $1,170.30