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	$167.54	6.854%	$179.0232	$179.02	$179.00	$179.00
Purchase #2	$18.57	10.846%	$20.5841	$20.58	$20.60	$20.60
Purchase #3	$86.64	7.156%	$92.84	$92.84	$92.85	$92.80
Purchase #4	$89.96	5.614%	$95.0104	$95.01	$95.00	$95.00
Purchase #5	$240.47	10.763%	$266.3518	$266.35	$266.35	$266.40
Purchase #6	$183.77	9.233%	$200.7375	$200.74	$200.75	$200.70
Purchase #7	$231.42	8.527%	$251.1532	$251.15	$251.15	$251.20
7 purchase totals =	$1,018.37		$1,105.7002	$1,105.69	$1,105.70	$1,105.70