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 $212.60   5.344%   $223.9613   $223.96   $223.95   $224.00  
  Purchase #2 $210.58   11.768%   $235.3611   $235.36   $235.35   $235.40  
  Purchase #3 $191.97   11.157%   $213.3881   $213.39   $213.40   $213.40  
  Purchase #4 $117.67   8.386%   $127.5378   $127.54   $127.55   $127.50  
  Purchase #5 $135.51   10.804%   $150.1505   $150.15   $150.15   $150.20  
  Purchase #6 $45.76   12.764%   $51.6008   $51.60   $51.60   $51.60  
  Purchase #7 $192.66   3.382%   $199.1758   $199.18   $199.20   $199.20  
  7 purchase totals = $1,106.75       $1,201.1754   $1,201.18   $1,201.20   $1,201.30