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	$33.35	5.413%	$35.1552	$35.16	$35.15	$35.20
Purchase #2	$154.39	5.267%	$162.5217	$162.52	$162.50	$162.50
Purchase #3	$72.98	6.335%	$77.6033	$77.60	$77.60	$77.60
Purchase #4	$155.75	3.118%	$160.6063	$160.61	$160.60	$160.60
Purchase #5	$128.66	10.454%	$142.1101	$142.11	$142.10	$142.10
Purchase #6	$165.65	6.120%	$175.7878	$175.79	$175.80	$175.80
Purchase #7	$157.65	4.772%	$165.1731	$165.17	$165.15	$165.20
7 purchase totals =	$868.43		$918.9575	$918.96	$918.90	$919.00