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 $89.56   3.559%   $92.7474   $92.75   $92.75   $92.70  
  Purchase #2 $132.78   6.721%   $141.7041   $141.70   $141.70   $141.70  
  Purchase #3 $196.79   4.768%   $206.1729   $206.17   $206.15   $206.20  
  Purchase #4 $127.58   7.541%   $137.2008   $137.20   $137.20   $137.20  
  Purchase #5 $51.86   7.131%   $55.5581   $55.56   $55.55   $55.60  
  Purchase #6 $128.73   3.287%   $132.9614   $132.96   $132.95   $133.00  
  Purchase #7 $44.64   4.196%   $46.5131   $46.51   $46.50   $46.50  
  7 purchase totals = $771.94       $812.8578   $812.85   $812.80   $812.90