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 $44.25   4.290%   $46.1483   $46.15   $46.15   $46.10  
  Purchase #2 $217.74   8.290%   $235.7906   $235.79   $235.80   $235.80  
  Purchase #3 $167.86   10.579%   $185.6179   $185.62   $185.60   $185.60  
  Purchase #4 $108.88   4.551%   $113.8351   $113.84   $113.85   $113.80  
  Purchase #5 $120.71   11.301%   $134.3514   $134.35   $134.35   $134.40  
  Purchase #6 $200.59   3.682%   $207.9757   $207.98   $208.00   $208.00  
  Purchase #7 $54.38   7.131%   $58.2578   $58.26   $58.25   $58.30  
  7 purchase totals = $914.41       $981.9768   $981.99   $982.00   $982.00