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	$110.78	3.443%	$114.5942	$114.59	$114.60	$114.60
Purchase #2	$72.46	5.839%	$76.6909	$76.69	$76.70	$76.70
Purchase #3	$141.67	8.147%	$153.2119	$153.21	$153.20	$153.20
Purchase #4	$53.87	10.552%	$59.5544	$59.55	$59.55	$59.60
Purchase #5	$74.62	8.234%	$80.7642	$80.76	$80.75	$80.80
Purchase #6	$138.60	7.766%	$149.3637	$149.36	$149.35	$149.40
Purchase #7	$151.86	10.340%	$167.5623	$167.56	$167.55	$167.60
7 purchase totals =	$743.86		$801.7416	$801.72	$801.70	$801.90