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	$94.49	7.514%	$101.59	$101.59	$101.60	$101.60
Purchase #2	$94.44	12.399%	$106.1496	$106.15	$106.15	$106.10
Purchase #3	$200.77	13.443%	$227.7595	$227.76	$227.75	$227.80
Purchase #4	$38.94	11.694%	$43.4936	$43.49	$43.50	$43.50
Purchase #5	$237.57	11.769%	$265.5296	$265.53	$265.55	$265.50
Purchase #6	$109.77	7.572%	$118.0818	$118.08	$118.10	$118.10
Purchase #7	$52.52	9.466%	$57.4915	$57.49	$57.50	$57.50
7 purchase totals =	$828.50		$920.0956	$920.09	$920.15	$920.10