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 $115.48   8.206%   $124.9563   $124.96   $124.95   $125.00  
  Purchase #2 $178.35   7.841%   $192.3344   $192.33   $192.35   $192.30  
  Purchase #3 $53.47   9.121%   $58.347   $58.35   $58.35   $58.30  
  Purchase #4 $82.56   4.800%   $86.5229   $86.52   $86.50   $86.50  
  Purchase #5 $142.66   7.411%   $153.2325   $153.23   $153.25   $153.20  
  Purchase #6 $233.44   5.763%   $246.8931   $246.89   $246.90   $246.90  
  Purchase #7 $190.93   5.519%   $201.4674   $201.47   $201.45   $201.50  
  7 purchase totals = $996.89       $1,063.7536   $1,063.75   $1,063.75   $1,063.70