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	$119.47	6.652%	$127.4171	$127.42	$127.40	$127.40
Purchase #2	$86.57	11.593%	$96.6061	$96.61	$96.60	$96.60
Purchase #3	$43.91	9.638%	$48.142	$48.14	$48.15	$48.10
Purchase #4	$95.82	7.799%	$103.293	$103.29	$103.30	$103.30
Purchase #5	$218.40	8.525%	$237.0186	$237.02	$237.00	$237.00
Purchase #6	$52.27	9.359%	$57.1619	$57.16	$57.15	$57.20
Purchase #7	$140.41	9.289%	$153.4527	$153.45	$153.45	$153.50
7 purchase totals =	$756.85		$823.0914	$823.09	$823.05	$823.10