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 $61.26   13.432%   $69.4884   $69.49   $69.50   $69.50  
  Purchase #2 $192.93   6.735%   $205.9238   $205.92   $205.90   $205.90  
  Purchase #3 $120.84   10.113%   $133.0605   $133.06   $133.05   $133.10  
  Purchase #4 $95.48   13.774%   $108.6314   $108.63   $108.65   $108.60  
  Purchase #5 $89.97   11.821%   $100.6054   $100.61   $100.60   $100.60  
  Purchase #6 $195.25   4.358%   $203.759   $203.76   $203.75   $203.80  
  Purchase #7 $244.89   11.306%   $272.5773   $272.58   $272.60   $272.60  
  7 purchase totals = $1,000.62       $1,094.0458   $1,094.05   $1,094.05   $1,094.10