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 $59.96   5.236%   $63.0995   $63.10   $63.10   $63.10  
  Purchase #2 $200.76   7.708%   $216.2346   $216.23   $216.25   $216.20  
  Purchase #3 $234.90   3.521%   $243.1708   $243.17   $243.15   $243.20  
  Purchase #4 $73.99   4.537%   $77.3469   $77.35   $77.35   $77.30  
  Purchase #5 $249.50   6.607%   $265.9845   $265.98   $266.00   $266.00  
  Purchase #6 $171.92   8.803%   $187.0541   $187.05   $187.05   $187.10  
  Purchase #7 $134.77   10.841%   $149.3804   $149.38   $149.40   $149.40  
  7 purchase totals = $1,125.80       $1,202.2708   $1,202.26   $1,202.30   $1,202.30