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	$127.72	13.406%	$144.8421	$144.84	$144.85	$144.80
Purchase #2	$57.80	10.851%	$64.0719	$64.07	$64.05	$64.10
Purchase #3	$230.42	13.764%	$262.135	$262.14	$262.15	$262.10
Purchase #4	$242.31	11.335%	$269.7758	$269.78	$269.80	$269.80
Purchase #5	$103.30	7.778%	$111.3347	$111.33	$111.35	$111.30
Purchase #6	$145.32	11.517%	$162.0565	$162.06	$162.05	$162.10
Purchase #7	$97.40	3.120%	$100.4389	$100.44	$100.45	$100.40
7 purchase totals =	$1,004.27		$1,114.6549	$1,114.66	$1,114.70	$1,114.60