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	$250.83	4.793%	$262.8523	$262.85	$262.85	$262.90
Purchase #2	$27.51	4.759%	$28.8192	$28.82	$28.80	$28.80
Purchase #3	$202.80	13.539%	$230.2571	$230.26	$230.25	$230.30
Purchase #4	$237.85	11.590%	$265.4168	$265.42	$265.40	$265.40
Purchase #5	$223.29	12.679%	$251.6009	$251.60	$251.60	$251.60
Purchase #6	$76.92	5.179%	$80.9037	$80.90	$80.90	$80.90
Purchase #7	$57.88	13.749%	$65.8379	$65.84	$65.85	$65.80
7 purchase totals =	$1,077.08		$1,185.6879	$1,185.69	$1,185.65	$1,185.70