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	$52.84	3.702%	$54.7961	$54.80	$54.80	$54.80
Purchase #2	$233.53	4.819%	$244.7838	$244.78	$244.80	$244.80
Purchase #3	$102.59	3.151%	$105.8226	$105.82	$105.80	$105.80
Purchase #4	$182.87	3.228%	$188.773	$188.77	$188.75	$188.80
Purchase #5	$205.89	6.103%	$218.4555	$218.46	$218.45	$218.50
Purchase #6	$179.30	10.395%	$197.9382	$197.94	$197.95	$197.90
Purchase #7	$5.80	12.577%	$6.5295	$6.53	$6.55	$6.50
7 purchase totals =	$962.82		$1,017.0987	$1,017.10	$1,017.10	$1,017.10