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	$137.94	5.601%	$145.666	$145.67	$145.65	$145.70
Purchase #2	$171.43	12.242%	$192.4165	$192.42	$192.40	$192.40
Purchase #3	$34.98	10.377%	$38.6099	$38.61	$38.60	$38.60
Purchase #4	$165.70	4.299%	$172.8234	$172.82	$172.80	$172.80
Purchase #5	$173.78	13.155%	$196.6408	$196.64	$196.65	$196.60
Purchase #6	$241.83	7.115%	$259.0362	$259.04	$259.05	$259.00
Purchase #7	$41.73	13.244%	$47.2567	$47.26	$47.25	$47.30
7 purchase totals =	$967.39		$1,052.4495	$1,052.46	$1,052.40	$1,052.40