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 $34.82   3.554%   $36.0575   $36.06   $36.05   $36.10  
  Purchase #2 $194.58   5.623%   $205.5212   $205.52   $205.50   $205.50  
  Purchase #3 $247.32   3.641%   $256.3249   $256.32   $256.30   $256.30  
  Purchase #4 $52.40   13.318%   $59.3786   $59.38   $59.40   $59.40  
  Purchase #5 $189.61   13.747%   $215.6757   $215.68   $215.70   $215.70  
  Purchase #6 $204.49   3.416%   $211.4754   $211.48   $211.50   $211.50  
  Purchase #7 $140.58   3.544%   $145.5622   $145.56   $145.55   $145.60  
  7 purchase totals = $1,063.80       $1,129.9955   $1,130.00   $1,130.00   $1,130.10