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	$179.90	10.742%	$199.2249	$199.22	$199.20	$199.20
Purchase #2	$55.75	13.222%	$63.1213	$63.12	$63.10	$63.10
Purchase #3	$172.54	8.746%	$187.6303	$187.63	$187.65	$187.60
Purchase #4	$197.91	9.559%	$216.8282	$216.83	$216.85	$216.80
Purchase #5	$212.45	12.469%	$238.9404	$238.94	$238.95	$238.90
Purchase #6	$56.75	9.817%	$62.3211	$62.32	$62.30	$62.30
Purchase #7	$91.80	13.238%	$103.9525	$103.95	$103.95	$104.00
7 purchase totals =	$967.10		$1,072.0187	$1,072.01	$1,072.00	$1,071.90