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	$127.26	13.242%	$144.1118	$144.11	$144.10	$144.10
Purchase #2	$39.36	7.346%	$42.2514	$42.25	$42.25	$42.30
Purchase #3	$78.54	6.379%	$83.5501	$83.55	$83.55	$83.60
Purchase #4	$204.50	4.568%	$213.8416	$213.84	$213.85	$213.80
Purchase #5	$103.80	5.760%	$109.7789	$109.78	$109.80	$109.80
Purchase #6	$66.41	3.358%	$68.64	$68.64	$68.65	$68.60
Purchase #7	$205.75	13.611%	$233.7546	$233.75	$233.75	$233.80
7 purchase totals =	$825.62		$895.9284	$895.92	$895.95	$896.00