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 $95.64   3.148%   $98.6507   $98.65   $98.65   $98.70  
  Purchase #2 $144.69   3.852%   $150.2635   $150.26   $150.25   $150.30  
  Purchase #3 $54.42   10.867%   $60.3338   $60.33   $60.35   $60.30  
  Purchase #4 $156.66   13.600%   $177.9658   $177.97   $177.95   $178.00  
  Purchase #5 $233.87   13.577%   $265.6225   $265.62   $265.60   $265.60  
  Purchase #6 $119.95   12.355%   $134.7698   $134.77   $134.75   $134.80  
  Purchase #7 $122.58   5.561%   $129.3967   $129.40   $129.40   $129.40  
  7 purchase totals = $927.81       $1,017.0028   $1,017.00   $1,016.95   $1,017.10