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 $122.69   3.183%   $126.5952   $126.60   $126.60   $126.60  
  Purchase #2 $84.43   4.852%   $88.5265   $88.53   $88.55   $88.50  
  Purchase #3 $206.69   8.562%   $224.3868   $224.39   $224.40   $224.40  
  Purchase #4 $161.90   13.528%   $183.8018   $183.80   $183.80   $183.80  
  Purchase #5 $56.76   10.740%   $62.856   $62.86   $62.85   $62.90  
  Purchase #6 $155.85   10.714%   $172.5478   $172.55   $172.55   $172.50  
  Purchase #7 $245.84   4.865%   $257.8001   $257.80   $257.80   $257.80  
  7 purchase totals = $1,034.16       $1,116.5142   $1,116.53   $1,116.55   $1,116.50