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	$181.86	9.728%	$199.5513	$199.55	$199.55	$199.60
Purchase #2	$103.37	9.637%	$113.3318	$113.33	$113.35	$113.30
Purchase #3	$127.50	5.435%	$134.4296	$134.43	$134.45	$134.40
Purchase #4	$136.69	6.396%	$145.4327	$145.43	$145.45	$145.40
Purchase #5	$145.79	3.281%	$150.5734	$150.57	$150.55	$150.60
Purchase #6	$48.37	12.780%	$54.5517	$54.55	$54.55	$54.60
Purchase #7	$104.84	12.617%	$118.0677	$118.07	$118.05	$118.10
7 purchase totals =	$848.42		$915.9382	$915.93	$915.95	$916.00