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 $58.76   7.276%   $63.0354   $63.04   $63.05   $63.00  
  Purchase #2 $56.72   8.169%   $61.3535   $61.35   $61.35   $61.40  
  Purchase #3 $232.37   12.171%   $260.6518   $260.65   $260.65   $260.70  
  Purchase #4 $166.97   7.311%   $179.1772   $179.18   $179.20   $179.20  
  Purchase #5 $114.42   3.632%   $118.5757   $118.58   $118.60   $118.60  
  Purchase #6 $179.68   8.792%   $195.4775   $195.48   $195.50   $195.50  
  Purchase #7 $194.27   7.754%   $209.3337   $209.33   $209.35   $209.30  
  7 purchase totals = $1,003.19       $1,087.6048   $1,087.61   $1,087.70   $1,087.70