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 $57.85   5.198%   $60.857   $60.86   $60.85   $60.90  
  Purchase #2 $250.72   10.523%   $277.1033   $277.10   $277.10   $277.10  
  Purchase #3 $54.60   7.791%   $58.8539   $58.85   $58.85   $58.90  
  Purchase #4 $92.86   9.580%   $101.756   $101.76   $101.75   $101.80  
  Purchase #5 $187.25   4.445%   $195.5733   $195.57   $195.55   $195.60  
  Purchase #6 $7.65   11.613%   $8.5384   $8.54   $8.55   $8.50  
  Purchase #7 $248.76   4.816%   $260.7403   $260.74   $260.75   $260.70  
  7 purchase totals = $899.69       $963.4222   $963.42   $963.40   $963.50