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 $85.38   13.210%   $96.6587   $96.66   $96.65   $96.70  
  Purchase #2 $219.55   3.363%   $226.9335   $226.93   $226.95   $226.90  
  Purchase #3 $135.61   9.207%   $148.0956   $148.10   $148.10   $148.10  
  Purchase #4 $58.96   4.693%   $61.727   $61.73   $61.75   $61.70  
  Purchase #5 $234.64   13.321%   $265.8964   $265.90   $265.90   $265.90  
  Purchase #6 $229.43   4.332%   $239.3689   $239.37   $239.35   $239.40  
  Purchase #7 $49.95   13.453%   $56.6698   $56.67   $56.65   $56.70  
  7 purchase totals = $1,013.52       $1,095.3499   $1,095.36   $1,095.35   $1,095.40