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 $91.82   4.614%   $96.0566   $96.06   $96.05   $96.10  
  Purchase #2 $103.62   11.301%   $115.3301   $115.33   $115.35   $115.30  
  Purchase #3 $32.71   10.144%   $36.0281   $36.03   $36.05   $36.00  
  Purchase #4 $144.31   5.132%   $151.716   $151.72   $151.70   $151.70  
  Purchase #5 $81.96   3.725%   $85.013   $85.01   $85.00   $85.00  
  Purchase #6 $30.61   3.299%   $31.6198   $31.62   $31.60   $31.60  
  Purchase #7 $239.85   4.774%   $251.3004   $251.30   $251.30   $251.30  
  7 purchase totals = $724.88       $767.0640   $767.07   $767.05   $767.00