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	$55.42	7.441%	$59.5438	$59.54	$59.55	$59.50
Purchase #2	$172.85	6.202%	$183.5702	$183.57	$183.55	$183.60
Purchase #3	$154.78	6.776%	$165.2679	$165.27	$165.25	$165.30
Purchase #4	$231.52	10.456%	$255.7277	$255.73	$255.75	$255.70
Purchase #5	$142.98	3.105%	$147.4195	$147.42	$147.40	$147.40
Purchase #6	$180.77	13.454%	$205.0908	$205.09	$205.10	$205.10
Purchase #7	$52.77	10.334%	$58.2233	$58.22	$58.20	$58.20
7 purchase totals =	$991.09		$1,074.8432	$1,074.84	$1,074.80	$1,074.80