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	$216.34	4.149%	$225.3159	$225.32	$225.30	$225.30
Purchase #2	$9.72	5.446%	$10.2494	$10.25	$10.25	$10.20
Purchase #3	$166.54	10.458%	$183.9568	$183.96	$183.95	$184.00
Purchase #4	$131.86	3.646%	$136.6676	$136.67	$136.65	$136.70
Purchase #5	$158.27	13.501%	$179.638	$179.64	$179.65	$179.60
Purchase #6	$66.83	7.839%	$72.0688	$72.07	$72.05	$72.10
Purchase #7	$20.98	11.130%	$23.3151	$23.32	$23.30	$23.30
7 purchase totals =	$770.54		$831.2116	$831.23	$831.15	$831.20