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 $48.55   10.511%   $53.6531   $53.65   $53.65   $53.70  
  Purchase #2 $158.35   3.342%   $163.6421   $163.64   $163.65   $163.60  
  Purchase #3 $185.66   3.392%   $191.9576   $191.96   $191.95   $192.00  
  Purchase #4 $83.66   11.207%   $93.0358   $93.04   $93.05   $93.00  
  Purchase #5 $13.86   6.563%   $14.7696   $14.77   $14.75   $14.80  
  Purchase #6 $162.32   4.509%   $169.639   $169.64   $169.65   $169.60  
  Purchase #7 $160.65   7.189%   $172.1991   $172.20   $172.20   $172.20  
  7 purchase totals = $813.05       $858.8963   $858.90   $858.90   $858.90