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 $58.26   6.751%   $62.1931   $62.19   $62.20   $62.20  
  Purchase #2 $191.97   6.627%   $204.6919   $204.69   $204.70   $204.70  
  Purchase #3 $200.32   10.697%   $221.7482   $221.75   $221.75   $221.70  
  Purchase #4 $239.90   3.515%   $248.3325   $248.33   $248.35   $248.30  
  Purchase #5 $158.81   4.416%   $165.823   $165.82   $165.80   $165.80  
  Purchase #6 $169.55   13.639%   $192.6749   $192.67   $192.65   $192.70  
  Purchase #7 $94.61   9.405%   $103.5081   $103.51   $103.50   $103.50  
  7 purchase totals = $1,113.42       $1,198.9717   $1,198.96   $1,198.95   $1,198.90