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	$105.53	10.159%	$116.2508	$116.25	$116.25	$116.30
Purchase #2	$223.72	4.364%	$233.4831	$233.48	$233.50	$233.50
Purchase #3	$91.37	4.781%	$95.7384	$95.74	$95.75	$95.70
Purchase #4	$226.52	3.273%	$233.934	$233.93	$233.95	$233.90
Purchase #5	$63.93	3.359%	$66.0774	$66.08	$66.10	$66.10
Purchase #6	$141.80	3.612%	$146.9218	$146.92	$146.90	$146.90
Purchase #7	$166.68	7.841%	$179.7494	$179.75	$179.75	$179.70
7 purchase totals =	$1,019.55		$1,072.1549	$1,072.15	$1,072.20	$1,072.10