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	$125.89	6.855%	$134.5198	$134.52	$134.50	$134.50
Purchase #2	$152.50	9.451%	$166.9128	$166.91	$166.90	$166.90
Purchase #3	$176.45	10.811%	$195.526	$195.53	$195.55	$195.50
Purchase #4	$74.95	13.634%	$85.1687	$85.17	$85.15	$85.20
Purchase #5	$77.88	9.478%	$85.2615	$85.26	$85.25	$85.30
Purchase #6	$114.27	3.370%	$118.1209	$118.12	$118.10	$118.10
Purchase #7	$214.82	3.653%	$222.6674	$222.67	$222.65	$222.70
7 purchase totals =	$936.76		$1,008.1771	$1,008.18	$1,008.10	$1,008.20