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 $93.34   5.743%   $98.7005   $98.70   $98.70   $98.70  
  Purchase #2 $127.81   3.781%   $132.6425   $132.64   $132.65   $132.60  
  Purchase #3 $168.81   11.519%   $188.2552   $188.26   $188.25   $188.30  
  Purchase #4 $210.54   10.845%   $233.3731   $233.37   $233.35   $233.40  
  Purchase #5 $174.35   6.777%   $186.1657   $186.17   $186.15   $186.20  
  Purchase #6 $22.25   4.672%   $23.2895   $23.29   $23.30   $23.30  
  Purchase #7 $170.35   11.827%   $190.4973   $190.50   $190.50   $190.50  
  7 purchase totals = $967.45       $1,052.9238   $1,052.93   $1,052.90   $1,053.00