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 $57.54   4.357%   $60.047   $60.05   $60.05   $60.00  
  Purchase #2 $201.41   9.643%   $220.832   $220.83   $220.85   $220.80  
  Purchase #3 $241.92   3.513%   $250.4186   $250.42   $250.40   $250.40  
  Purchase #4 $53.96   6.433%   $57.4312   $57.43   $57.45   $57.40  
  Purchase #5 $213.79   5.612%   $225.7879   $225.79   $225.80   $225.80  
  Purchase #6 $209.71   12.809%   $236.5718   $236.57   $236.55   $236.60  
  Purchase #7 $96.30   6.262%   $102.3303   $102.33   $102.35   $102.30  
  7 purchase totals = $1,074.63       $1,153.4188   $1,153.42   $1,153.45   $1,153.30