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	$216.78	5.254%	$228.1696	$228.17	$228.15	$228.20
Purchase #2	$41.59	5.152%	$43.7327	$43.73	$43.75	$43.70
Purchase #3	$74.50	4.188%	$77.6201	$77.62	$77.60	$77.60
Purchase #4	$243.27	11.422%	$271.0563	$271.06	$271.05	$271.10
Purchase #5	$36.85	6.713%	$39.3237	$39.32	$39.30	$39.30
Purchase #6	$203.49	11.123%	$226.1242	$226.12	$226.10	$226.10
Purchase #7	$173.59	6.829%	$185.4445	$185.44	$185.45	$185.40
7 purchase totals =	$990.07		$1,071.4711	$1,071.46	$1,071.40	$1,071.40