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	$142.37	3.652%	$147.5694	$147.57	$147.55	$147.60
Purchase #2	$124.63	8.217%	$134.8708	$134.87	$134.85	$134.90
Purchase #3	$161.39	13.835%	$183.7183	$183.72	$183.70	$183.70
Purchase #4	$58.94	4.233%	$61.4349	$61.43	$61.45	$61.40
Purchase #5	$155.32	13.268%	$175.9279	$175.93	$175.95	$175.90
Purchase #6	$178.42	10.241%	$196.692	$196.69	$196.70	$196.70
Purchase #7	$159.78	4.578%	$167.0947	$167.09	$167.10	$167.10
7 purchase totals =	$980.85		$1,067.3080	$1,067.30	$1,067.30	$1,067.30