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 $62.49   13.176%   $70.7237   $70.72   $70.70   $70.70  
  Purchase #2 $233.95   3.689%   $242.5804   $242.58   $242.60   $242.60  
  Purchase #3 $101.56   13.502%   $115.2726   $115.27   $115.25   $115.30  
  Purchase #4 $226.75   6.362%   $241.1758   $241.18   $241.20   $241.20  
  Purchase #5 $33.51   10.755%   $37.114   $37.11   $37.10   $37.10  
  Purchase #6 $22.65   10.637%   $25.0593   $25.06   $25.05   $25.10  
  Purchase #7 $32.63   7.454%   $35.0622   $35.06   $35.05   $35.10  
  7 purchase totals = $713.54       $766.9880   $766.98   $766.95   $767.10