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 $95.67   8.397%   $103.7034   $103.70   $103.70   $103.70  
  Purchase #2 $68.89   11.405%   $76.7469   $76.75   $76.75   $76.70  
  Purchase #3 $234.28   13.616%   $266.1796   $266.18   $266.20   $266.20  
  Purchase #4 $207.86   12.103%   $233.0173   $233.02   $233.00   $233.00  
  Purchase #5 $54.83   13.639%   $62.3083   $62.31   $62.30   $62.30  
  Purchase #6 $219.87   9.705%   $241.2084   $241.21   $241.20   $241.20  
  Purchase #7 $221.94   10.481%   $245.2015   $245.20   $245.20   $245.20  
  7 purchase totals = $1,103.34       $1,228.3654   $1,228.37   $1,228.35   $1,228.30