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 $89.66   6.647%   $95.6197   $95.62   $95.60   $95.60  
  Purchase #2 $14.44   3.178%   $14.8989   $14.90   $14.90   $14.90  
  Purchase #3 $59.32   10.852%   $65.7574   $65.76   $65.75   $65.80  
  Purchase #4 $224.91   4.689%   $235.456   $235.46   $235.45   $235.50  
  Purchase #5 $167.82   4.466%   $175.3148   $175.31   $175.30   $175.30  
  Purchase #6 $212.87   10.575%   $235.381   $235.38   $235.40   $235.40  
  Purchase #7 $43.38   8.562%   $47.0942   $47.09   $47.10   $47.10  
  7 purchase totals = $812.40       $869.5220   $869.52   $869.50   $869.60