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	$9.39	11.172%	$10.4391	$10.44	$10.45	$10.40
Purchase #2	$184.64	10.642%	$204.2894	$204.29	$204.30	$204.30
Purchase #3	$52.51	13.601%	$59.6519	$59.65	$59.65	$59.70
Purchase #4	$92.53	10.850%	$102.5695	$102.57	$102.55	$102.60
Purchase #5	$215.50	8.440%	$233.6882	$233.69	$233.70	$233.70
Purchase #6	$111.94	13.856%	$127.4504	$127.45	$127.45	$127.50
Purchase #7	$236.91	12.122%	$265.6282	$265.63	$265.65	$265.60
7 purchase totals =	$903.42		$1,003.7167	$1,003.72	$1,003.75	$1,003.80