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	$107.51	3.702%	$111.49	$111.49	$111.50	$111.50
Purchase #2	$240.92	10.480%	$266.1684	$266.17	$266.15	$266.20
Purchase #3	$91.58	5.128%	$96.2762	$96.28	$96.30	$96.30
Purchase #4	$111.83	7.575%	$120.3011	$120.30	$120.30	$120.30
Purchase #5	$96.53	7.859%	$104.1163	$104.12	$104.10	$104.10
Purchase #6	$56.43	10.673%	$62.4528	$62.45	$62.45	$62.50
Purchase #7	$211.72	7.293%	$227.1607	$227.16	$227.15	$227.20
7 purchase totals =	$916.52		$987.9655	$987.97	$987.95	$988.10