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 $195.31   5.317%   $205.6946   $205.69   $205.70   $205.70  
  Purchase #2 $147.37   4.189%   $153.5433   $153.54   $153.55   $153.50  
  Purchase #3 $75.84   13.608%   $86.1603   $86.16   $86.15   $86.20  
  Purchase #4 $32.90   6.842%   $35.151   $35.15   $35.15   $35.20  
  Purchase #5 $195.78   5.791%   $207.1176   $207.12   $207.10   $207.10  
  Purchase #6 $126.58   5.776%   $133.8913   $133.89   $133.90   $133.90  
  Purchase #7 $186.85   13.828%   $212.6876   $212.69   $212.70   $212.70  
  7 purchase totals = $960.63       $1,034.2457   $1,034.24   $1,034.25   $1,034.30