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	$217.72	3.248%	$224.7915	$224.79	$224.80	$224.80
Purchase #2	$87.72	5.415%	$92.47	$92.47	$92.45	$92.50
Purchase #3	$85.42	13.458%	$96.9158	$96.92	$96.90	$96.90
Purchase #4	$190.29	3.375%	$196.7123	$196.71	$196.70	$196.70
Purchase #5	$195.63	8.451%	$212.1627	$212.16	$212.15	$212.20
Purchase #6	$178.40	10.601%	$197.3122	$197.31	$197.30	$197.30
Purchase #7	$107.27	3.735%	$111.2765	$111.28	$111.30	$111.30
7 purchase totals =	$1,062.45		$1,131.6410	$1,131.64	$1,131.60	$1,131.70