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	$166.75	4.517%	$174.2821	$174.28	$174.30	$174.30
Purchase #2	$49.86	12.172%	$55.929	$55.93	$55.95	$55.90
Purchase #3	$167.65	13.839%	$190.8511	$190.85	$190.85	$190.90
Purchase #4	$13.62	9.421%	$14.9031	$14.90	$14.90	$14.90
Purchase #5	$114.52	8.322%	$124.0504	$124.05	$124.05	$124.10
Purchase #6	$168.38	10.170%	$185.5042	$185.50	$185.50	$185.50
Purchase #7	$10.33	7.501%	$11.1049	$11.10	$11.10	$11.10
7 purchase totals =	$691.11		$756.6248	$756.61	$756.65	$756.70