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	$81.46	13.231%	$92.238	$92.24	$92.25	$92.20
Purchase #2	$201.98	5.206%	$212.4951	$212.50	$212.50	$212.50
Purchase #3	$51.96	3.161%	$53.6025	$53.60	$53.60	$53.60
Purchase #4	$49.83	13.414%	$56.5142	$56.51	$56.50	$56.50
Purchase #5	$150.90	3.565%	$156.2796	$156.28	$156.30	$156.30
Purchase #6	$39.45	6.669%	$42.0809	$42.08	$42.10	$42.10
Purchase #7	$160.98	12.694%	$181.4148	$181.41	$181.40	$181.40
7 purchase totals =	$736.56		$794.6251	$794.62	$794.65	$794.60