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 $174.61   11.819%   $195.2472   $195.25   $195.25   $195.20  
  Purchase #2 $7.69   4.126%   $8.0073   $8.01   $8.00   $8.00  
  Purchase #3 $226.79   6.842%   $242.307   $242.31   $242.30   $242.30  
  Purchase #4 $130.42   7.779%   $140.5654   $140.57   $140.55   $140.60  
  Purchase #5 $153.26   12.348%   $172.1845   $172.18   $172.20   $172.20  
  Purchase #6 $153.50   5.438%   $161.8473   $161.85   $161.85   $161.80  
  Purchase #7 $171.61   8.785%   $186.6859   $186.69   $186.70   $186.70  
  7 purchase totals = $1,017.88       $1,106.8446   $1,106.86   $1,106.85   $1,106.80