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	$54.83	9.332%	$59.9467	$59.95	$59.95	$59.90
Purchase #2	$181.76	12.853%	$205.1216	$205.12	$205.10	$205.10
Purchase #3	$21.52	4.328%	$22.4514	$22.45	$22.45	$22.50
Purchase #4	$66.57	8.191%	$72.0227	$72.02	$72.00	$72.00
Purchase #5	$65.37	6.375%	$69.5373	$69.54	$69.55	$69.50
Purchase #6	$53.69	4.441%	$56.0744	$56.07	$56.05	$56.10
Purchase #7	$91.88	5.511%	$96.9435	$96.94	$96.95	$96.90
7 purchase totals =	$535.62		$582.0976	$582.09	$582.05	$582.00