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	$210.37	3.422%	$217.5689	$217.57	$217.55	$217.60
Purchase #2	$108.87	13.813%	$123.9082	$123.91	$123.90	$123.90
Purchase #3	$100.75	10.634%	$111.4638	$111.46	$111.45	$111.50
Purchase #4	$146.33	13.464%	$166.0319	$166.03	$166.05	$166.00
Purchase #5	$146.76	10.447%	$162.092	$162.09	$162.10	$162.10
Purchase #6	$209.80	8.153%	$226.905	$226.91	$226.90	$226.90
Purchase #7	$53.56	10.617%	$59.2465	$59.25	$59.25	$59.20
7 purchase totals =	$976.44		$1,067.2163	$1,067.22	$1,067.20	$1,067.20