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 $177.84   10.400%   $196.3354   $196.34   $196.35   $196.30  
  Purchase #2 $249.97   8.234%   $270.5525   $270.55   $270.55   $270.60  
  Purchase #3 $34.85   8.143%   $37.6878   $37.69   $37.70   $37.70  
  Purchase #4 $83.34   13.618%   $94.6892   $94.69   $94.70   $94.70  
  Purchase #5 $141.43   13.521%   $160.5528   $160.55   $160.55   $160.60  
  Purchase #6 $161.25   12.609%   $181.582   $181.58   $181.60   $181.60  
  Purchase #7 $91.28   3.288%   $94.2813   $94.28   $94.30   $94.30  
  7 purchase totals = $939.96       $1,035.6810   $1,035.68   $1,035.75   $1,035.80