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	$242.40	6.171%	$257.3585	$257.36	$257.35	$257.40
Purchase #2	$243.74	7.855%	$262.8858	$262.89	$262.90	$262.90
Purchase #3	$74.30	6.745%	$79.3115	$79.31	$79.30	$79.30
Purchase #4	$40.57	5.439%	$42.7766	$42.78	$42.80	$42.80
Purchase #5	$138.90	5.155%	$146.0603	$146.06	$146.05	$146.10
Purchase #6	$165.32	4.672%	$173.0438	$173.04	$173.05	$173.00
Purchase #7	$225.62	13.413%	$255.8824	$255.88	$255.90	$255.90
7 purchase totals =	$1,130.85		$1,217.3189	$1,217.32	$1,217.35	$1,217.40