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 $243.96   6.585%   $260.0248   $260.02   $260.00   $260.00  
  Purchase #2 $76.92   12.834%   $86.7919   $86.79   $86.80   $86.80  
  Purchase #3 $50.30   3.134%   $51.8764   $51.88   $51.90   $51.90  
  Purchase #4 $188.98   3.135%   $194.9045   $194.90   $194.90   $194.90  
  Purchase #5 $206.47   3.477%   $213.649   $213.65   $213.65   $213.60  
  Purchase #6 $76.50   13.685%   $86.969   $86.97   $86.95   $87.00  
  Purchase #7 $203.78   5.144%   $214.2624   $214.26   $214.25   $214.30  
  7 purchase totals = $1,046.91       $1,108.4780   $1,108.47   $1,108.45   $1,108.50