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	$161.68	8.592%	$175.5715	$175.57	$175.55	$175.60
Purchase #2	$5.90	7.184%	$6.3239	$6.32	$6.30	$6.30
Purchase #3	$111.41	6.264%	$118.3887	$118.39	$118.40	$118.40
Purchase #4	$122.60	12.171%	$137.5216	$137.52	$137.50	$137.50
Purchase #5	$130.86	5.383%	$137.9042	$137.90	$137.90	$137.90
Purchase #6	$138.95	8.769%	$151.1345	$151.13	$151.15	$151.10
Purchase #7	$70.91	10.123%	$78.0882	$78.09	$78.10	$78.10
7 purchase totals =	$742.31		$804.9326	$804.92	$804.90	$804.90