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	$29.64	11.548%	$33.0628	$33.06	$33.05	$33.10
Purchase #2	$83.88	8.339%	$90.8748	$90.87	$90.85	$90.90
Purchase #3	$176.52	9.184%	$192.7316	$192.73	$192.75	$192.70
Purchase #4	$33.94	13.805%	$38.6254	$38.63	$38.65	$38.60
Purchase #5	$136.54	4.321%	$142.4399	$142.44	$142.45	$142.40
Purchase #6	$190.54	7.774%	$205.3526	$205.35	$205.35	$205.40
Purchase #7	$159.79	13.784%	$181.8155	$181.82	$181.80	$181.80
7 purchase totals =	$810.85		$884.9026	$884.90	$884.90	$884.90