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 $60.35   4.737%   $63.2088   $63.21   $63.20   $63.20  
  Purchase #2 $227.81   3.640%   $236.1023   $236.10   $236.10   $236.10  
  Purchase #3 $138.61   6.163%   $147.1525   $147.15   $147.15   $147.20  
  Purchase #4 $103.59   4.434%   $108.1832   $108.18   $108.20   $108.20  
  Purchase #5 $178.89   13.830%   $203.6305   $203.63   $203.65   $203.60  
  Purchase #6 $184.67   3.325%   $190.8103   $190.81   $190.80   $190.80  
  Purchase #7 $140.35   8.502%   $152.2826   $152.28   $152.30   $152.30  
  7 purchase totals = $1,034.27       $1,101.3702   $1,101.36   $1,101.40   $1,101.40