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 $235.85   6.844%   $251.9916   $251.99   $252.00   $252.00  
  Purchase #2 $199.50   13.684%   $226.7996   $226.80   $226.80   $226.80  
  Purchase #3 $189.33   7.786%   $204.0712   $204.07   $204.05   $204.10  
  Purchase #4 $105.67   9.743%   $115.9654   $115.97   $115.95   $116.00  
  Purchase #5 $111.43   11.756%   $124.5297   $124.53   $124.55   $124.50  
  Purchase #6 $81.78   5.683%   $86.4276   $86.43   $86.45   $86.40  
  Purchase #7 $13.65   4.561%   $14.2726   $14.27   $14.25   $14.30  
  7 purchase totals = $937.21       $1,024.0577   $1,024.06   $1,024.05   $1,024.10