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 $202.97   5.118%   $213.358   $213.36   $213.35   $213.40  
  Purchase #2 $12.98   8.365%   $14.0658   $14.07   $14.05   $14.10  
  Purchase #3 $44.30   3.837%   $45.9998   $46.00   $46.00   $46.00  
  Purchase #4 $102.83   5.628%   $108.6173   $108.62   $108.60   $108.60  
  Purchase #5 $72.95   3.261%   $75.3289   $75.33   $75.35   $75.30  
  Purchase #6 $176.29   9.839%   $193.6352   $193.64   $193.65   $193.60  
  Purchase #7 $91.88   10.367%   $101.4052   $101.41   $101.40   $101.40  
  7 purchase totals = $704.20       $752.4102   $752.43   $752.40   $752.40