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	$38.81	12.472%	$43.6504	$43.65	$43.65	$43.70
Purchase #2	$161.28	3.379%	$166.7297	$166.73	$166.75	$166.70
Purchase #3	$123.34	3.664%	$127.8592	$127.86	$127.85	$127.90
Purchase #4	$245.40	10.151%	$270.3106	$270.31	$270.30	$270.30
Purchase #5	$115.66	6.422%	$123.0877	$123.09	$123.10	$123.10
Purchase #6	$110.57	4.498%	$115.5434	$115.54	$115.55	$115.50
Purchase #7	$104.81	5.255%	$110.3178	$110.32	$110.30	$110.30
7 purchase totals =	$899.87		$957.4988	$957.50	$957.50	$957.50