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	$180.75	8.558%	$196.2186	$196.22	$196.20	$196.20
Purchase #2	$116.82	3.209%	$120.5688	$120.57	$120.55	$120.60
Purchase #3	$238.52	11.828%	$266.7321	$266.73	$266.75	$266.70
Purchase #4	$166.76	11.255%	$185.5288	$185.53	$185.55	$185.50
Purchase #5	$174.26	4.172%	$181.5301	$181.53	$181.55	$181.50
Purchase #6	$247.75	12.411%	$278.4983	$278.50	$278.50	$278.50
Purchase #7	$192.64	7.581%	$207.244	$207.24	$207.25	$207.20
7 purchase totals =	$1,317.50		$1,436.3207	$1,436.32	$1,436.35	$1,436.20