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 $194.70   3.682%   $201.8689   $201.87   $201.85   $201.90  
  Purchase #2 $39.86   11.639%   $44.4993   $44.50   $44.50   $44.50  
  Purchase #3 $144.88   8.739%   $157.5411   $157.54   $157.55   $157.50  
  Purchase #4 $98.79   5.763%   $104.4833   $104.48   $104.50   $104.50  
  Purchase #5 $190.97   7.366%   $205.0369   $205.04   $205.05   $205.00  
  Purchase #6 $214.68   4.264%   $223.834   $223.83   $223.85   $223.80  
  Purchase #7 $90.59   5.805%   $95.8487   $95.85   $95.85   $95.80  
  7 purchase totals = $974.47       $1,033.1122   $1,033.11   $1,033.15   $1,033.00