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 $60.96   4.267%   $63.5612   $63.56   $63.55   $63.60  
  Purchase #2 $175.88   3.365%   $181.7984   $181.80   $181.80   $181.80  
  Purchase #3 $88.53   3.211%   $91.3727   $91.37   $91.35   $91.40  
  Purchase #4 $233.35   13.623%   $265.1393   $265.14   $265.15   $265.10  
  Purchase #5 $89.52   5.205%   $94.1795   $94.18   $94.20   $94.20  
  Purchase #6 $12.46   13.764%   $14.175   $14.18   $14.20   $14.20  
  Purchase #7 $166.35   11.642%   $185.7165   $185.72   $185.70   $185.70  
  7 purchase totals = $827.05       $895.9426   $895.95   $895.95   $896.00