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 $65.48   7.827%   $70.6051   $70.61   $70.60   $70.60  
  Purchase #2 $57.94   11.328%   $64.5034   $64.50   $64.50   $64.50  
  Purchase #3 $159.38   3.700%   $165.2771   $165.28   $165.30   $165.30  
  Purchase #4 $46.98   7.746%   $50.6191   $50.62   $50.60   $50.60  
  Purchase #5 $250.75   5.874%   $265.4791   $265.48   $265.50   $265.50  
  Purchase #6 $168.36   8.213%   $182.1874   $182.19   $182.20   $182.20  
  Purchase #7 $230.65   7.122%   $247.0769   $247.08   $247.10   $247.10  
  7 purchase totals = $979.54       $1,045.7481   $1,045.76   $1,045.80   $1,045.80