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	$138.64	9.688%	$152.0714	$152.07	$152.05	$152.10
Purchase #2	$133.52	10.809%	$147.9522	$147.95	$147.95	$148.00
Purchase #3	$142.30	7.675%	$153.2215	$153.22	$153.20	$153.20
Purchase #4	$49.69	7.809%	$53.5703	$53.57	$53.55	$53.60
Purchase #5	$91.57	5.256%	$96.3829	$96.38	$96.40	$96.40
Purchase #6	$240.51	3.304%	$248.4565	$248.46	$248.45	$248.50
Purchase #7	$205.25	13.618%	$233.2009	$233.20	$233.20	$233.20
7 purchase totals =	$1,001.48		$1,084.8557	$1,084.85	$1,084.80	$1,085.00