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 $60.64   7.627%   $65.265   $65.27   $65.25   $65.30  
  Purchase #2 $101.30   10.548%   $111.9851   $111.99   $112.00   $112.00  
  Purchase #3 $110.33   9.551%   $120.8676   $120.87   $120.85   $120.90  
  Purchase #4 $94.90   9.540%   $103.9535   $103.95   $103.95   $104.00  
  Purchase #5 $113.28   9.805%   $124.3871   $124.39   $124.40   $124.40  
  Purchase #6 $175.91   11.202%   $195.6154   $195.62   $195.60   $195.60  
  Purchase #7 $58.99   9.343%   $64.5014   $64.50   $64.50   $64.50  
  7 purchase totals = $715.35       $786.5751   $786.59   $786.55   $786.70