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	$233.68	13.421%	$265.0422	$265.04	$265.05	$265.00
Purchase #2	$49.31	9.225%	$53.8588	$53.86	$53.85	$53.90
Purchase #3	$195.79	10.262%	$215.882	$215.88	$215.90	$215.90
Purchase #4	$23.86	8.139%	$25.802	$25.80	$25.80	$25.80
Purchase #5	$151.82	10.857%	$168.3031	$168.30	$168.30	$168.30
Purchase #6	$234.55	4.619%	$245.3839	$245.38	$245.40	$245.40
Purchase #7	$162.79	5.326%	$171.4602	$171.46	$171.45	$171.50
7 purchase totals =	$1,051.80		$1,145.7322	$1,145.72	$1,145.75	$1,145.80