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 $88.33   11.114%   $98.147   $98.15   $98.15   $98.10  
  Purchase #2 $182.42   4.268%   $190.2057   $190.21   $190.20   $190.20  
  Purchase #3 $209.81   4.502%   $219.2556   $219.26   $219.25   $219.30  
  Purchase #4 $248.44   5.850%   $262.9737   $262.97   $262.95   $263.00  
  Purchase #5 $196.75   3.700%   $204.0298   $204.03   $204.05   $204.00  
  Purchase #6 $185.38   3.764%   $192.3577   $192.36   $192.35   $192.40  
  Purchase #7 $225.62   12.568%   $253.9759   $253.98   $254.00   $254.00  
  7 purchase totals = $1,336.75       $1,420.9454   $1,420.96   $1,420.95   $1,421.00