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 $86.85   11.251%   $96.6215   $96.62   $96.60   $96.60  
  Purchase #2 $248.73   7.745%   $267.9941   $267.99   $268.00   $268.00  
  Purchase #3 $91.67   3.496%   $94.8748   $94.87   $94.85   $94.90  
  Purchase #4 $19.44   3.184%   $20.059   $20.06   $20.05   $20.10  
  Purchase #5 $215.99   10.416%   $238.4875   $238.49   $238.50   $238.50  
  Purchase #6 $206.49   13.831%   $235.0496   $235.05   $235.05   $235.00  
  Purchase #7 $56.60   8.798%   $61.5797   $61.58   $61.60   $61.60  
  7 purchase totals = $925.77       $1,014.6662   $1,014.66   $1,014.65   $1,014.70