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	$9.83	7.655%	$10.5825	$10.58	$10.60	$10.60
Purchase #2	$184.94	10.481%	$204.3236	$204.32	$204.30	$204.30
Purchase #3	$44.60	4.164%	$46.4571	$46.46	$46.45	$46.50
Purchase #4	$223.27	6.618%	$238.046	$238.05	$238.05	$238.00
Purchase #5	$35.78	12.630%	$40.299	$40.30	$40.30	$40.30
Purchase #6	$176.79	11.125%	$196.4579	$196.46	$196.45	$196.50
Purchase #7	$37.95	6.560%	$40.4395	$40.44	$40.45	$40.40
7 purchase totals =	$713.16		$776.6056	$776.61	$776.60	$776.60