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 $199.76   5.500%   $210.7468   $210.75   $210.75   $210.70  
  Purchase #2 $201.80   5.446%   $212.79   $212.79   $212.80   $212.80  
  Purchase #3 $9.87   9.118%   $10.7699   $10.77   $10.75   $10.80  
  Purchase #4 $190.81   12.113%   $213.9228   $213.92   $213.90   $213.90  
  Purchase #5 $70.98   13.765%   $80.7504   $80.75   $80.75   $80.80  
  Purchase #6 $104.92   12.451%   $117.9836   $117.98   $118.00   $118.00  
  Purchase #7 $215.64   10.418%   $238.1054   $238.11   $238.10   $238.10  
  7 purchase totals = $993.78       $1,085.0689   $1,085.07   $1,085.05   $1,085.10