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 $60.60   4.238%   $63.1682   $63.17   $63.15   $63.20  
  Purchase #2 $153.74   8.838%   $167.3275   $167.33   $167.35   $167.30  
  Purchase #3 $52.68   4.435%   $55.0164   $55.02   $55.00   $55.00  
  Purchase #4 $8.92   8.462%   $9.6748   $9.67   $9.65   $9.70  
  Purchase #5 $149.53   13.361%   $169.5087   $169.51   $169.50   $169.50  
  Purchase #6 $74.49   9.749%   $81.752   $81.75   $81.75   $81.80  
  Purchase #7 $207.62   5.724%   $219.5042   $219.50   $219.50   $219.50  
  7 purchase totals = $707.58       $765.9518   $765.95   $765.90   $766.00