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	$150.84	11.849%	$168.713	$168.71	$168.70	$168.70
Purchase #2	$157.78	9.820%	$173.274	$173.27	$173.25	$173.30
Purchase #3	$223.69	6.454%	$238.127	$238.13	$238.15	$238.10
Purchase #4	$149.45	8.441%	$162.0651	$162.07	$162.05	$162.10
Purchase #5	$191.61	4.418%	$200.0753	$200.08	$200.10	$200.10
Purchase #6	$71.83	11.154%	$79.8419	$79.84	$79.85	$79.80
Purchase #7	$18.83	3.566%	$19.5015	$19.50	$19.50	$19.50
7 purchase totals =	$964.03		$1,041.5978	$1,041.60	$1,041.60	$1,041.60