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	$154.45	9.318%	$168.8417	$168.84	$168.85	$168.80
Purchase #2	$109.89	6.735%	$117.2911	$117.29	$117.30	$117.30
Purchase #3	$117.64	8.228%	$127.3194	$127.32	$127.30	$127.30
Purchase #4	$183.61	5.714%	$194.1015	$194.10	$194.10	$194.10
Purchase #5	$100.80	9.521%	$110.3972	$110.40	$110.40	$110.40
Purchase #6	$157.72	8.730%	$171.489	$171.49	$171.50	$171.50
Purchase #7	$144.45	12.189%	$162.057	$162.06	$162.05	$162.10
7 purchase totals =	$968.56		$1,051.4969	$1,051.50	$1,051.50	$1,051.50