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 $119.75   4.824%   $125.5267   $125.53   $125.55   $125.50  
  Purchase #2 $192.47   8.305%   $208.4546   $208.45   $208.45   $208.50  
  Purchase #3 $157.87   9.424%   $172.7477   $172.75   $172.75   $172.70  
  Purchase #4 $59.90   4.570%   $62.6374   $62.64   $62.65   $62.60  
  Purchase #5 $166.32   13.799%   $189.2705   $189.27   $189.25   $189.30  
  Purchase #6 $128.97   12.227%   $144.7392   $144.74   $144.75   $144.70  
  Purchase #7 $59.84   7.272%   $64.1916   $64.19   $64.20   $64.20  
  7 purchase totals = $885.12       $967.5677   $967.57   $967.60   $967.50