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	$161.89	6.175%	$171.8867	$171.89	$171.90	$171.90
Purchase #2	$177.89	10.483%	$196.5382	$196.54	$196.55	$196.50
Purchase #3	$167.60	6.606%	$178.6717	$178.67	$178.65	$178.70
Purchase #4	$45.56	5.517%	$48.0735	$48.07	$48.05	$48.10
Purchase #5	$208.30	13.163%	$235.7185	$235.72	$235.70	$235.70
Purchase #6	$233.75	10.458%	$258.1956	$258.20	$258.20	$258.20
Purchase #7	$52.96	5.549%	$55.8988	$55.90	$55.90	$55.90
7 purchase totals =	$1,047.95		$1,144.9830	$1,144.99	$1,144.95	$1,145.00