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	$200.60	11.379%	$223.4263	$223.43	$223.45	$223.40
Purchase #2	$143.42	11.459%	$159.8545	$159.85	$159.85	$159.90
Purchase #3	$58.26	4.364%	$60.8025	$60.80	$60.80	$60.80
Purchase #4	$117.54	12.564%	$132.3077	$132.31	$132.30	$132.30
Purchase #5	$65.74	8.107%	$71.0695	$71.07	$71.05	$71.10
Purchase #6	$35.30	8.435%	$38.2776	$38.28	$38.30	$38.30
Purchase #7	$98.57	10.627%	$109.045	$109.05	$109.05	$109.00
7 purchase totals =	$719.43		$794.7831	$794.79	$794.80	$794.80