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	$134.39	6.764%	$143.4801	$143.48	$143.50	$143.50
Purchase #2	$141.73	10.610%	$156.7676	$156.77	$156.75	$156.80
Purchase #3	$182.85	9.456%	$200.1403	$200.14	$200.15	$200.10
Purchase #4	$174.57	11.672%	$194.9458	$194.95	$194.95	$194.90
Purchase #5	$180.84	13.493%	$205.2407	$205.24	$205.25	$205.20
Purchase #6	$141.54	7.798%	$152.5773	$152.58	$152.60	$152.60
Purchase #7	$208.44	12.218%	$233.9072	$233.91	$233.90	$233.90
7 purchase totals =	$1,164.36		$1,287.0590	$1,287.07	$1,287.10	$1,287.00