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 $203.97   3.452%   $211.011   $211.01   $211.00   $211.00  
  Purchase #2 $214.37   10.335%   $236.5251   $236.53   $236.55   $236.50  
  Purchase #3 $65.39   5.195%   $68.787   $68.79   $68.80   $68.80  
  Purchase #4 $44.26   11.464%   $49.334   $49.33   $49.35   $49.30  
  Purchase #5 $115.74   10.214%   $127.5617   $127.56   $127.55   $127.60  
  Purchase #6 $201.84   3.413%   $208.7288   $208.73   $208.75   $208.70  
  Purchase #7 $175.46   6.198%   $186.335   $186.34   $186.35   $186.30  
  7 purchase totals = $1,021.03       $1,088.2826   $1,088.29   $1,088.35   $1,088.20