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 $179.75   8.855%   $195.6669   $195.67   $195.65   $195.70  
  Purchase #2 $187.71   6.802%   $200.478   $200.48   $200.50   $200.50  
  Purchase #3 $79.55   6.669%   $84.8552   $84.86   $84.85   $84.90  
  Purchase #4 $160.97   5.852%   $170.39   $170.39   $170.40   $170.40  
  Purchase #5 $200.88   6.564%   $214.0658   $214.07   $214.05   $214.10  
  Purchase #6 $13.46   5.773%   $14.237   $14.24   $14.25   $14.20  
  Purchase #7 $128.37   12.757%   $144.7462   $144.75   $144.75   $144.70  
  7 purchase totals = $950.69       $1,024.4391   $1,024.46   $1,024.45   $1,024.50