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 $186.26   3.313%   $192.4308   $192.43   $192.45   $192.40  
  Purchase #2 $173.89   13.125%   $196.7131   $196.71   $196.70   $196.70  
  Purchase #3 $232.29   4.200%   $242.0462   $242.05   $242.05   $242.00  
  Purchase #4 $245.61   12.721%   $276.854   $276.85   $276.85   $276.90  
  Purchase #5 $9.51   10.701%   $10.5277   $10.53   $10.55   $10.50  
  Purchase #6 $184.41   7.315%   $197.8996   $197.90   $197.90   $197.90  
  Purchase #7 $147.25   3.775%   $152.8087   $152.81   $152.80   $152.80  
  7 purchase totals = $1,179.22       $1,269.2801   $1,269.28   $1,269.30   $1,269.20