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	$138.70	5.219%	$145.9388	$145.94	$145.95	$145.90
Purchase #2	$194.82	5.144%	$204.8415	$204.84	$204.85	$204.80
Purchase #3	$206.97	9.866%	$227.3897	$227.39	$227.40	$227.40
Purchase #4	$181.54	9.575%	$198.9225	$198.92	$198.90	$198.90
Purchase #5	$157.50	5.538%	$166.2224	$166.22	$166.20	$166.20
Purchase #6	$58.64	4.281%	$61.1504	$61.15	$61.15	$61.20
Purchase #7	$69.42	3.509%	$71.8559	$71.86	$71.85	$71.90
7 purchase totals =	$1,007.59		$1,076.3212	$1,076.32	$1,076.30	$1,076.30