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 $176.48   10.148%   $194.3892   $194.39   $194.40   $194.40  
  Purchase #2 $158.38   8.496%   $171.836   $171.84   $171.85   $171.80  
  Purchase #3 $15.95   4.376%   $16.648   $16.65   $16.65   $16.60  
  Purchase #4 $245.92   9.576%   $269.4693   $269.47   $269.45   $269.50  
  Purchase #5 $116.76   10.286%   $128.7699   $128.77   $128.75   $128.80  
  Purchase #6 $66.41   13.174%   $75.1589   $75.16   $75.15   $75.20  
  Purchase #7 $169.91   3.569%   $175.9741   $175.97   $175.95   $176.00  
  7 purchase totals = $949.81       $1,032.2454   $1,032.25   $1,032.20   $1,032.30