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	$230.36	11.330%	$256.4598	$256.46	$256.45	$256.50
Purchase #2	$101.39	4.736%	$106.1918	$106.19	$106.20	$106.20
Purchase #3	$53.32	3.641%	$55.2614	$55.26	$55.25	$55.30
Purchase #4	$23.72	5.810%	$25.0981	$25.10	$25.10	$25.10
Purchase #5	$128.50	9.770%	$141.0545	$141.05	$141.05	$141.10
Purchase #6	$80.81	12.269%	$90.7246	$90.72	$90.70	$90.70
Purchase #7	$11.57	10.333%	$12.7655	$12.77	$12.75	$12.80
7 purchase totals =	$629.67		$687.5557	$687.55	$687.50	$687.70