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	$102.38	9.335%	$111.9372	$111.94	$111.95	$111.90
Purchase #2	$142.82	10.667%	$158.0546	$158.05	$158.05	$158.10
Purchase #3	$65.25	9.524%	$71.4644	$71.46	$71.45	$71.50
Purchase #4	$237.37	12.818%	$267.7961	$267.80	$267.80	$267.80
Purchase #5	$214.50	11.777%	$239.7617	$239.76	$239.75	$239.80
Purchase #6	$242.55	13.474%	$275.2312	$275.23	$275.25	$275.20
Purchase #7	$94.37	8.783%	$102.6585	$102.66	$102.65	$102.70
7 purchase totals =	$1,099.24		$1,226.9037	$1,226.90	$1,226.90	$1,227.00