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	$135.81	7.140%	$145.5068	$145.51	$145.50	$145.50
Purchase #2	$100.35	11.390%	$111.7799	$111.78	$111.80	$111.80
Purchase #3	$102.52	12.797%	$115.6395	$115.64	$115.65	$115.60
Purchase #4	$231.33	4.466%	$241.6612	$241.66	$241.65	$241.70
Purchase #5	$73.77	11.741%	$82.4313	$82.43	$82.45	$82.40
Purchase #6	$73.82	5.775%	$78.0831	$78.08	$78.10	$78.10
Purchase #7	$96.92	3.323%	$100.1407	$100.14	$100.15	$100.10
7 purchase totals =	$814.52		$875.2425	$875.24	$875.30	$875.20