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 $214.60   10.286%   $236.6738   $236.67   $236.65   $236.70  
  Purchase #2 $63.69   5.782%   $67.3726   $67.37   $67.35   $67.40  
  Purchase #3 $48.29   13.152%   $54.6411   $54.64   $54.65   $54.60  
  Purchase #4 $187.41   12.840%   $211.4734   $211.47   $211.45   $211.50  
  Purchase #5 $226.33   3.494%   $234.238   $234.24   $234.25   $234.20  
  Purchase #6 $145.69   10.844%   $161.4886   $161.49   $161.50   $161.50  
  Purchase #7 $119.35   6.119%   $126.653   $126.65   $126.65   $126.70  
  7 purchase totals = $1,005.36       $1,092.5405   $1,092.53   $1,092.50   $1,092.60