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	$150.50	11.580%	$167.9279	$167.93	$167.95	$167.90
Purchase #2	$152.41	3.337%	$157.4959	$157.50	$157.50	$157.50
Purchase #3	$11.93	13.263%	$13.5123	$13.51	$13.50	$13.50
Purchase #4	$189.44	13.397%	$214.8193	$214.82	$214.80	$214.80
Purchase #5	$118.83	12.474%	$133.6529	$133.65	$133.65	$133.70
Purchase #6	$63.60	13.333%	$72.0798	$72.08	$72.10	$72.10
Purchase #7	$220.79	9.867%	$242.5753	$242.58	$242.60	$242.60
7 purchase totals =	$907.50		$1,002.0634	$1,002.07	$1,002.10	$1,002.10