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 $58.94   3.834%   $61.1998   $61.20   $61.20   $61.20  
  Purchase #2 $138.33   10.294%   $152.5697   $152.57   $152.55   $152.60  
  Purchase #3 $22.48   9.557%   $24.6284   $24.63   $24.65   $24.60  
  Purchase #4 $196.38   5.135%   $206.4641   $206.46   $206.45   $206.50  
  Purchase #5 $212.53   6.868%   $227.1266   $227.13   $227.15   $227.10  
  Purchase #6 $237.41   13.575%   $269.6384   $269.64   $269.65   $269.60  
  Purchase #7 $141.48   7.781%   $152.4886   $152.49   $152.50   $152.50  
  7 purchase totals = $1,007.55       $1,094.1156   $1,094.12   $1,094.15   $1,094.10