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 $58.61   4.553%   $61.2785   $61.28   $61.30   $61.30  
  Purchase #2 $185.42   4.541%   $193.8399   $193.84   $193.85   $193.80  
  Purchase #3 $192.47   8.282%   $208.4104   $208.41   $208.40   $208.40  
  Purchase #4 $215.79   3.420%   $223.17   $223.17   $223.15   $223.20  
  Purchase #5 $229.39   7.774%   $247.2228   $247.22   $247.20   $247.20  
  Purchase #6 $5.70   4.184%   $5.9385   $5.94   $5.95   $5.90  
  Purchase #7 $189.33   12.287%   $212.593   $212.59   $212.60   $212.60  
  7 purchase totals = $1,076.71       $1,152.4531   $1,152.45   $1,152.45   $1,152.40