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	$173.87	13.774%	$197.8189	$197.82	$197.80	$197.80
Purchase #2	$110.98	6.588%	$118.2914	$118.29	$118.30	$118.30
Purchase #3	$62.64	5.239%	$65.9217	$65.92	$65.90	$65.90
Purchase #4	$214.86	6.829%	$229.5328	$229.53	$229.55	$229.50
Purchase #5	$221.33	4.746%	$231.8343	$231.83	$231.85	$231.80
Purchase #6	$99.48	12.417%	$111.8324	$111.83	$111.85	$111.80
Purchase #7	$198.65	3.228%	$205.0624	$205.06	$205.05	$205.10
7 purchase totals =	$1,081.81		$1,160.2939	$1,160.28	$1,160.30	$1,160.20