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	$118.43	12.740%	$133.518	$133.52	$133.50	$133.50
Purchase #2	$111.60	6.498%	$118.8518	$118.85	$118.85	$118.90
Purchase #3	$43.98	12.125%	$49.3126	$49.31	$49.30	$49.30
Purchase #4	$187.88	7.187%	$201.3829	$201.38	$201.40	$201.40
Purchase #5	$106.52	4.312%	$111.1131	$111.11	$111.10	$111.10
Purchase #6	$172.49	11.527%	$192.3729	$192.37	$192.35	$192.40
Purchase #7	$183.98	3.282%	$190.0182	$190.02	$190.00	$190.00
7 purchase totals =	$924.88		$996.5695	$996.56	$996.50	$996.60