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	$51.94	4.496%	$54.2752	$54.28	$54.30	$54.30
Purchase #2	$133.89	6.138%	$142.1082	$142.11	$142.10	$142.10
Purchase #3	$177.77	5.812%	$188.102	$188.10	$188.10	$188.10
Purchase #4	$25.78	12.729%	$29.0615	$29.06	$29.05	$29.10
Purchase #5	$139.37	8.758%	$151.576	$151.58	$151.60	$151.60
Purchase #6	$153.63	12.322%	$172.5603	$172.56	$172.55	$172.60
Purchase #7	$23.41	5.571%	$24.7142	$24.71	$24.70	$24.70
7 purchase totals =	$705.79		$762.3974	$762.40	$762.40	$762.50