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	$24.79	3.465%	$25.649	$25.65	$25.65	$25.60
Purchase #2	$230.57	10.148%	$253.9682	$253.97	$253.95	$254.00
Purchase #3	$89.99	6.528%	$95.8645	$95.86	$95.85	$95.90
Purchase #4	$151.38	11.450%	$168.713	$168.71	$168.70	$168.70
Purchase #5	$142.86	6.361%	$151.9473	$151.95	$151.95	$151.90
Purchase #6	$42.25	9.763%	$46.3749	$46.37	$46.35	$46.40
Purchase #7	$47.61	13.551%	$54.0616	$54.06	$54.05	$54.10
7 purchase totals =	$729.45		$796.5785	$796.57	$796.50	$796.60