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	$168.75	9.773%	$185.2419	$185.24	$185.25	$185.20
Purchase #2	$164.78	9.570%	$180.5494	$180.55	$180.55	$180.50
Purchase #3	$38.64	13.683%	$43.9271	$43.93	$43.95	$43.90
Purchase #4	$128.46	13.450%	$145.7379	$145.74	$145.75	$145.70
Purchase #5	$87.71	7.620%	$94.3935	$94.39	$94.40	$94.40
Purchase #6	$91.52	12.137%	$102.6278	$102.63	$102.65	$102.60
Purchase #7	$82.56	11.559%	$92.1031	$92.10	$92.10	$92.10
7 purchase totals =	$762.42		$844.5807	$844.58	$844.65	$844.40