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	$34.34	9.253%	$37.5175	$37.52	$37.50	$37.50
Purchase #2	$95.80	13.858%	$109.076	$109.08	$109.10	$109.10
Purchase #3	$30.96	3.565%	$32.0637	$32.06	$32.05	$32.10
Purchase #4	$183.77	3.618%	$190.4188	$190.42	$190.40	$190.40
Purchase #5	$220.60	4.619%	$230.7895	$230.79	$230.80	$230.80
Purchase #6	$211.88	9.163%	$231.2946	$231.29	$231.30	$231.30
Purchase #7	$211.75	5.148%	$222.6509	$222.65	$222.65	$222.70
7 purchase totals =	$989.10		$1,053.8110	$1,053.81	$1,053.80	$1,053.90