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	$219.84	6.523%	$234.1802	$234.18	$234.20	$234.20
Purchase #2	$182.92	3.379%	$189.1009	$189.10	$189.10	$189.10
Purchase #3	$193.62	8.741%	$210.5443	$210.54	$210.55	$210.50
Purchase #4	$184.55	5.271%	$194.2776	$194.28	$194.30	$194.30
Purchase #5	$30.98	3.560%	$32.0829	$32.08	$32.10	$32.10
Purchase #6	$109.32	3.241%	$112.8631	$112.86	$112.85	$112.90
Purchase #7	$41.42	5.169%	$43.561	$43.56	$43.55	$43.60
7 purchase totals =	$962.65		$1,016.6100	$1,016.60	$1,016.65	$1,016.70