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 $118.35   5.588%   $124.9634   $124.96   $124.95   $125.00  
  Purchase #2 $8.78   13.436%   $9.9597   $9.96   $9.95   $10.00  
  Purchase #3 $112.63   5.301%   $118.6005   $118.60   $118.60   $118.60  
  Purchase #4 $190.43   7.252%   $204.24   $204.24   $204.25   $204.20  
  Purchase #5 $159.63   4.168%   $166.2834   $166.28   $166.30   $166.30  
  Purchase #6 $198.71   5.439%   $209.5178   $209.52   $209.50   $209.50  
  Purchase #7 $174.69   5.345%   $184.0272   $184.03   $184.05   $184.00  
  7 purchase totals = $963.22       $1,017.5920   $1,017.59   $1,017.60   $1,017.60