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	$59.90	3.748%	$62.1451	$62.15	$62.15	$62.10
Purchase #2	$173.75	9.174%	$189.6898	$189.69	$189.70	$189.70
Purchase #3	$34.40	12.688%	$38.7647	$38.76	$38.75	$38.80
Purchase #4	$150.65	3.740%	$156.2843	$156.28	$156.30	$156.30
Purchase #5	$212.71	7.436%	$228.5271	$228.53	$228.55	$228.50
Purchase #6	$119.74	10.660%	$132.5043	$132.50	$132.50	$132.50
Purchase #7	$99.51	3.529%	$103.0217	$103.02	$103.00	$103.00
7 purchase totals =	$850.66		$910.9370	$910.93	$910.95	$910.90