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	$201.71	8.123%	$218.0949	$218.09	$218.10	$218.10
Purchase #2	$23.49	9.486%	$25.7183	$25.72	$25.70	$25.70
Purchase #3	$139.40	10.685%	$154.2949	$154.29	$154.30	$154.30
Purchase #4	$102.40	3.639%	$106.1263	$106.13	$106.15	$106.10
Purchase #5	$90.94	8.119%	$98.3234	$98.32	$98.30	$98.30
Purchase #6	$104.35	7.255%	$111.9206	$111.92	$111.90	$111.90
Purchase #7	$102.30	9.271%	$111.7842	$111.78	$111.80	$111.80
7 purchase totals =	$764.59		$826.2626	$826.25	$826.25	$826.20