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 $33.28   13.270%   $37.6963   $37.70   $37.70   $37.70  
  Purchase #2 $223.87   10.804%   $248.0569   $248.06   $248.05   $248.10  
  Purchase #3 $187.35   4.171%   $195.1644   $195.16   $195.15   $195.20  
  Purchase #4 $218.70   6.858%   $233.6984   $233.70   $233.70   $233.70  
  Purchase #5 $151.82   9.769%   $166.6513   $166.65   $166.65   $166.70  
  Purchase #6 $152.64   11.194%   $169.7265   $169.73   $169.75   $169.70  
  Purchase #7 $136.47   13.205%   $154.4909   $154.49   $154.50   $154.50  
  7 purchase totals = $1,104.13       $1,205.4847   $1,205.49   $1,205.50   $1,205.60