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	$116.49	6.597%	$124.1748	$124.17	$124.15	$124.20
Purchase #2	$227.31	7.185%	$243.6422	$243.64	$243.65	$243.60
Purchase #3	$177.50	10.768%	$196.6132	$196.61	$196.60	$196.60
Purchase #4	$153.30	12.467%	$172.4119	$172.41	$172.40	$172.40
Purchase #5	$178.94	8.853%	$194.7816	$194.78	$194.80	$194.80
Purchase #6	$92.83	8.696%	$100.9025	$100.90	$100.90	$100.90
Purchase #7	$11.84	12.514%	$13.3217	$13.32	$13.30	$13.30
7 purchase totals =	$958.21		$1,045.8479	$1,045.83	$1,045.80	$1,045.80