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	$114.25	5.659%	$120.7154	$120.72	$120.70	$120.70
Purchase #2	$78.78	7.287%	$84.5207	$84.52	$84.50	$84.50
Purchase #3	$12.83	13.511%	$14.5635	$14.56	$14.55	$14.60
Purchase #4	$151.63	13.328%	$171.8392	$171.84	$171.85	$171.80
Purchase #5	$47.93	13.493%	$54.3972	$54.40	$54.40	$54.40
Purchase #6	$10.29	11.646%	$11.4884	$11.49	$11.50	$11.50
Purchase #7	$61.75	5.525%	$65.1617	$65.16	$65.15	$65.20
7 purchase totals =	$477.46		$522.6861	$522.69	$522.65	$522.70