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	$89.57	10.865%	$99.3018	$99.30	$99.30	$99.30
Purchase #2	$102.93	8.428%	$111.6049	$111.60	$111.60	$111.60
Purchase #3	$132.55	7.187%	$142.0764	$142.08	$142.10	$142.10
Purchase #4	$75.94	13.780%	$86.4045	$86.40	$86.40	$86.40
Purchase #5	$51.67	10.151%	$56.915	$56.92	$56.90	$56.90
Purchase #6	$238.80	11.852%	$267.1026	$267.10	$267.10	$267.10
Purchase #7	$110.45	7.107%	$118.2997	$118.30	$118.30	$118.30
7 purchase totals =	$801.91		$881.7049	$881.70	$881.70	$881.70