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 $216.65   13.185%   $245.2153   $245.22   $245.20   $245.20  
  Purchase #2 $237.91   10.441%   $262.7502   $262.75   $262.75   $262.80  
  Purchase #3 $156.43   12.573%   $176.0979   $176.10   $176.10   $176.10  
  Purchase #4 $94.49   7.180%   $101.2744   $101.27   $101.25   $101.30  
  Purchase #5 $92.86   5.794%   $98.2403   $98.24   $98.25   $98.20  
  Purchase #6 $94.61   13.712%   $107.5829   $107.58   $107.60   $107.60  
  Purchase #7 $180.26   11.371%   $200.7574   $200.76   $200.75   $200.80  
  7 purchase totals = $1,073.21       $1,191.9184   $1,191.92   $1,191.90   $1,192.00