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	$105.44	6.816%	$112.6268	$112.63	$112.65	$112.60
Purchase #2	$166.30	8.196%	$179.9299	$179.93	$179.95	$179.90
Purchase #3	$104.68	9.298%	$114.4131	$114.41	$114.40	$114.40
Purchase #4	$145.60	11.691%	$162.6221	$162.62	$162.60	$162.60
Purchase #5	$52.86	13.704%	$60.1039	$60.10	$60.10	$60.10
Purchase #6	$37.61	13.757%	$42.784	$42.78	$42.80	$42.80
Purchase #7	$174.78	3.238%	$180.4394	$180.44	$180.45	$180.40
7 purchase totals =	$787.27		$852.9192	$852.91	$852.95	$852.80