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 $34.45   5.219%   $36.2479   $36.25   $36.25   $36.20  
  Purchase #2 $180.43   9.370%   $197.3363   $197.34   $197.35   $197.30  
  Purchase #3 $227.61   9.250%   $248.6639   $248.66   $248.65   $248.70  
  Purchase #4 $13.33   6.557%   $14.204   $14.20   $14.20   $14.20  
  Purchase #5 $169.90   5.779%   $179.7185   $179.72   $179.70   $179.70  
  Purchase #6 $250.75   11.464%   $279.496   $279.50   $279.50   $279.50  
  Purchase #7 $186.67   10.503%   $206.276   $206.28   $206.30   $206.30  
  7 purchase totals = $1,063.14       $1,161.9426   $1,161.95   $1,161.95   $1,161.90