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 $13.31   5.649%   $14.0619   $14.06   $14.05   $14.10  
  Purchase #2 $202.84   7.734%   $218.5276   $218.53   $218.55   $218.50  
  Purchase #3 $221.84   11.390%   $247.1076   $247.11   $247.10   $247.10  
  Purchase #4 $188.33   5.647%   $198.965   $198.97   $198.95   $199.00  
  Purchase #5 $53.86   10.186%   $59.3462   $59.35   $59.35   $59.30  
  Purchase #6 $23.58   4.627%   $24.671   $24.67   $24.65   $24.70  
  Purchase #7 $233.54   11.588%   $260.6026   $260.60   $260.60   $260.60  
  7 purchase totals = $937.30       $1,023.2819   $1,023.29   $1,023.25   $1,023.30