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	$111.30	3.260%	$114.9284	$114.93	$114.95	$114.90
Purchase #2	$67.31	10.542%	$74.4058	$74.41	$74.40	$74.40
Purchase #3	$88.86	6.257%	$94.42	$94.42	$94.40	$94.40
Purchase #4	$68.96	10.776%	$76.3911	$76.39	$76.40	$76.40
Purchase #5	$9.83	13.422%	$11.1494	$11.15	$11.15	$11.10
Purchase #6	$115.59	12.448%	$129.9786	$129.98	$130.00	$130.00
Purchase #7	$82.66	9.467%	$90.4854	$90.49	$90.50	$90.50
7 purchase totals =	$544.51		$591.7587	$591.77	$591.80	$591.70