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	$22.51	13.329%	$25.5104	$25.51	$25.50	$25.50
Purchase #2	$73.67	4.712%	$77.1413	$77.14	$77.15	$77.10
Purchase #3	$97.44	11.449%	$108.5959	$108.60	$108.60	$108.60
Purchase #4	$166.35	4.869%	$174.4496	$174.45	$174.45	$174.40
Purchase #5	$11.27	13.615%	$12.8044	$12.80	$12.80	$12.80
Purchase #6	$128.89	3.112%	$132.9011	$132.90	$132.90	$132.90
Purchase #7	$89.79	7.215%	$96.2683	$96.27	$96.25	$96.30
7 purchase totals =	$589.92		$627.6710	$627.67	$627.65	$627.60