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   11.449%   $67.5827   $67.58   $67.60   $67.60  
  Purchase #2 $171.69   12.248%   $192.7186   $192.72   $192.70   $192.70  
  Purchase #3 $104.86   5.780%   $110.9209   $110.92   $110.90   $110.90  
  Purchase #4 $63.43   4.559%   $66.3218   $66.32   $66.30   $66.30  
  Purchase #5 $138.26   6.782%   $147.6368   $147.64   $147.65   $147.60  
  Purchase #6 $116.69   12.759%   $131.5785   $131.58   $131.60   $131.60  
  Purchase #7 $210.34   13.305%   $238.3257   $238.33   $238.35   $238.30  
  7 purchase totals = $865.91       $955.0850   $955.09   $955.10   $955.00