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	$151.70	13.469%	$172.1325	$172.13	$172.15	$172.10
Purchase #2	$11.99	9.831%	$13.1687	$13.17	$13.15	$13.20
Purchase #3	$182.92	12.281%	$205.3844	$205.38	$205.40	$205.40
Purchase #4	$116.65	10.194%	$128.5413	$128.54	$128.55	$128.50
Purchase #5	$179.58	3.858%	$186.5082	$186.51	$186.50	$186.50
Purchase #6	$105.60	7.368%	$113.3806	$113.38	$113.40	$113.40
Purchase #7	$82.30	9.119%	$89.8049	$89.80	$89.80	$89.80
7 purchase totals =	$830.74		$908.9206	$908.91	$908.95	$908.90