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	$162.84	11.178%	$181.0423	$181.04	$181.05	$181.00
Purchase #2	$91.35	7.109%	$97.8441	$97.84	$97.85	$97.80
Purchase #3	$68.55	4.297%	$71.4956	$71.50	$71.50	$71.50
Purchase #4	$173.98	6.703%	$185.6419	$185.64	$185.65	$185.60
Purchase #5	$232.30	10.261%	$256.1363	$256.14	$256.15	$256.10
Purchase #6	$248.28	9.381%	$271.5711	$271.57	$271.55	$271.60
Purchase #7	$103.94	3.348%	$107.4199	$107.42	$107.40	$107.40
7 purchase totals =	$1,081.24		$1,171.1512	$1,171.15	$1,171.15	$1,171.00