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 $59.97   3.409%   $62.0144   $62.01   $62.00   $62.00  
  Purchase #2 $70.25   9.626%   $77.0123   $77.01   $77.00   $77.00  
  Purchase #3 $181.39   6.449%   $193.0878   $193.09   $193.10   $193.10  
  Purchase #4 $89.52   13.198%   $101.3348   $101.33   $101.35   $101.30  
  Purchase #5 $204.61   8.252%   $221.4944   $221.49   $221.50   $221.50  
  Purchase #6 $195.40   5.688%   $206.5144   $206.51   $206.50   $206.50  
  Purchase #7 $188.35   6.519%   $200.6285   $200.63   $200.65   $200.60  
  7 purchase totals = $989.49       $1,062.0866   $1,062.07   $1,062.10   $1,062.00