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	$118.98	7.159%	$127.4978	$127.50	$127.50	$127.50
Purchase #2	$160.72	11.443%	$179.1112	$179.11	$179.10	$179.10
Purchase #3	$179.43	3.497%	$185.7047	$185.70	$185.70	$185.70
Purchase #4	$116.43	3.180%	$120.1325	$120.13	$120.15	$120.10
Purchase #5	$177.60	8.521%	$192.7333	$192.73	$192.75	$192.70
Purchase #6	$66.83	8.202%	$72.3114	$72.31	$72.30	$72.30
Purchase #7	$229.40	5.320%	$241.6041	$241.60	$241.60	$241.60
7 purchase totals =	$1,049.39		$1,119.0950	$1,119.08	$1,119.10	$1,119.00