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	$118.77	4.121%	$123.6645	$123.66	$123.65	$123.70
Purchase #2	$65.87	13.776%	$74.9443	$74.94	$74.95	$74.90
Purchase #3	$174.80	7.470%	$187.8576	$187.86	$187.85	$187.90
Purchase #4	$70.54	4.371%	$73.6233	$73.62	$73.60	$73.60
Purchase #5	$172.81	9.403%	$189.0593	$189.06	$189.05	$189.10
Purchase #6	$169.78	13.415%	$192.556	$192.56	$192.55	$192.60
Purchase #7	$92.82	8.438%	$100.6522	$100.65	$100.65	$100.70
7 purchase totals =	$865.39		$942.3572	$942.35	$942.30	$942.50