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	$48.85	13.444%	$55.4174	$55.42	$55.40	$55.40
Purchase #2	$149.89	3.214%	$154.7075	$154.71	$154.70	$154.70
Purchase #3	$29.37	4.219%	$30.6091	$30.61	$30.60	$30.60
Purchase #4	$49.57	11.697%	$55.3682	$55.37	$55.35	$55.40
Purchase #5	$61.81	3.825%	$64.1742	$64.17	$64.15	$64.20
Purchase #6	$83.56	9.514%	$91.5099	$91.51	$91.50	$91.50
Purchase #7	$228.46	13.139%	$258.4774	$258.48	$258.50	$258.50
7 purchase totals =	$651.51		$710.2637	$710.27	$710.20	$710.30