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	$165.90	3.862%	$172.3071	$172.31	$172.30	$172.30
Purchase #2	$56.52	9.782%	$62.0488	$62.05	$62.05	$62.00
Purchase #3	$230.65	10.105%	$253.9572	$253.96	$253.95	$254.00
Purchase #4	$234.77	8.250%	$254.1385	$254.14	$254.15	$254.10
Purchase #5	$234.46	4.522%	$245.0623	$245.06	$245.05	$245.10
Purchase #6	$35.59	6.387%	$37.8631	$37.86	$37.85	$37.90
Purchase #7	$146.79	13.466%	$166.5567	$166.56	$166.55	$166.60
7 purchase totals =	$1,104.68		$1,191.9337	$1,191.94	$1,191.90	$1,192.00