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	$106.30	5.291%	$111.9243	$111.92	$111.90	$111.90
Purchase #2	$200.47	3.490%	$207.4664	$207.47	$207.45	$207.50
Purchase #3	$49.42	8.430%	$53.5861	$53.59	$53.60	$53.60
Purchase #4	$173.84	6.656%	$185.4108	$185.41	$185.40	$185.40
Purchase #5	$170.50	11.728%	$190.4962	$190.50	$190.50	$190.50
Purchase #6	$126.83	9.408%	$138.7622	$138.76	$138.75	$138.80
Purchase #7	$215.43	4.299%	$224.6913	$224.69	$224.70	$224.70
7 purchase totals =	$1,042.79		$1,112.3373	$1,112.34	$1,112.30	$1,112.40