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 $57.81   8.403%   $62.6678   $62.67   $62.65   $62.70  
  Purchase #2 $129.47   9.130%   $141.2906   $141.29   $141.30   $141.30  
  Purchase #3 $175.75   6.632%   $187.4057   $187.41   $187.40   $187.40  
  Purchase #4 $139.53   8.519%   $151.4166   $151.42   $151.40   $151.40  
  Purchase #5 $241.85   9.575%   $265.0071   $265.01   $265.00   $265.00  
  Purchase #6 $153.71   8.696%   $167.0766   $167.08   $167.10   $167.10  
  Purchase #7 $138.78   8.233%   $150.2058   $150.21   $150.20   $150.20  
  7 purchase totals = $1,036.90       $1,125.0702   $1,125.09   $1,125.05   $1,125.10