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 $62.87   13.720%   $71.4958   $71.50   $71.50   $71.50  
  Purchase #2 $93.87   10.367%   $103.6015   $103.60   $103.60   $103.60  
  Purchase #3 $210.98   4.355%   $220.1682   $220.17   $220.15   $220.20  
  Purchase #4 $232.60   11.697%   $259.8072   $259.81   $259.80   $259.80  
  Purchase #5 $70.60   8.141%   $76.3475   $76.35   $76.35   $76.30  
  Purchase #6 $12.72   12.469%   $14.3061   $14.31   $14.30   $14.30  
  Purchase #7 $108.65   9.260%   $118.711   $118.71   $118.70   $118.70  
  7 purchase totals = $792.29       $864.4373   $864.45   $864.40   $864.40