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 $177.58   10.260%   $195.7997   $195.80   $195.80   $195.80  
  Purchase #2 $210.38   4.267%   $219.3569   $219.36   $219.35   $219.40  
  Purchase #3 $93.91   7.398%   $100.8575   $100.86   $100.85   $100.90  
  Purchase #4 $178.34   9.641%   $195.5338   $195.53   $195.55   $195.50  
  Purchase #5 $205.88   10.268%   $227.0198   $227.02   $227.00   $227.00  
  Purchase #6 $49.38   4.116%   $51.4125   $51.41   $51.40   $51.40  
  Purchase #7 $203.99   11.102%   $226.637   $226.64   $226.65   $226.60  
  7 purchase totals = $1,119.46       $1,216.6172   $1,216.62   $1,216.60   $1,216.60