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	$80.60	8.735%	$87.6404	$87.64	$87.65	$87.60
Purchase #2	$222.53	13.124%	$251.7348	$251.73	$251.75	$251.70
Purchase #3	$242.27	5.492%	$255.5755	$255.58	$255.60	$255.60
Purchase #4	$115.96	13.819%	$131.9845	$131.98	$132.00	$132.00
Purchase #5	$79.75	3.123%	$82.2406	$82.24	$82.25	$82.20
Purchase #6	$200.90	3.650%	$208.2329	$208.23	$208.25	$208.20
Purchase #7	$128.72	3.162%	$132.7901	$132.79	$132.80	$132.80
7 purchase totals =	$1,070.73		$1,150.1988	$1,150.19	$1,150.30	$1,150.10