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 $112.61   11.860%   $125.9655   $125.97   $125.95   $126.00  
  Purchase #2 $165.34   3.457%   $171.0558   $171.06   $171.05   $171.10  
  Purchase #3 $33.40   11.443%   $37.222   $37.22   $37.20   $37.20  
  Purchase #4 $204.61   9.248%   $223.5323   $223.53   $223.55   $223.50  
  Purchase #5 $71.96   10.682%   $79.6468   $79.65   $79.65   $79.60  
  Purchase #6 $147.67   4.855%   $154.8394   $154.84   $154.85   $154.80  
  Purchase #7 $86.72   7.712%   $93.4078   $93.41   $93.40   $93.40  
  7 purchase totals = $822.31       $885.6696   $885.68   $885.65   $885.60