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	$228.93	5.485%	$241.4868	$241.49	$241.50	$241.50
Purchase #2	$198.75	5.464%	$209.6097	$209.61	$209.60	$209.60
Purchase #3	$151.75	10.112%	$167.095	$167.10	$167.10	$167.10
Purchase #4	$144.39	6.644%	$153.9833	$153.98	$154.00	$154.00
Purchase #5	$118.33	7.810%	$127.5716	$127.57	$127.55	$127.60
Purchase #6	$9.40	3.754%	$9.7529	$9.75	$9.75	$9.80
Purchase #7	$248.61	9.129%	$271.3056	$271.31	$271.30	$271.30
7 purchase totals =	$1,100.16		$1,180.8049	$1,180.81	$1,180.80	$1,180.90