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	$144.71	10.484%	$159.8814	$159.88	$159.90	$159.90
Purchase #2	$138.85	9.430%	$151.9436	$151.94	$151.95	$151.90
Purchase #3	$66.45	9.718%	$72.9076	$72.91	$72.90	$72.90
Purchase #4	$117.96	8.385%	$127.8509	$127.85	$127.85	$127.90
Purchase #5	$181.69	3.706%	$188.4234	$188.42	$188.40	$188.40
Purchase #6	$39.77	5.809%	$42.0802	$42.08	$42.10	$42.10
Purchase #7	$49.82	6.187%	$52.9024	$52.90	$52.90	$52.90
7 purchase totals =	$739.25		$795.9895	$795.98	$796.00	$796.00