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 $56.72   9.224%   $61.9519   $61.95   $61.95   $62.00  
  Purchase #2 $72.78   10.765%   $80.6148   $80.61   $80.60   $80.60  
  Purchase #3 $169.58   3.537%   $175.578   $175.58   $175.60   $175.60  
  Purchase #4 $195.84   13.161%   $221.6145   $221.61   $221.60   $221.60  
  Purchase #5 $58.55   11.581%   $65.3307   $65.33   $65.35   $65.30  
  Purchase #6 $155.29   13.626%   $176.4498   $176.45   $176.45   $176.40  
  Purchase #7 $230.55   7.392%   $247.5923   $247.59   $247.60   $247.60  
  7 purchase totals = $939.31       $1,029.1320   $1,029.12   $1,029.15   $1,029.10