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	$223.46	6.873%	$238.8184	$238.82	$238.80	$238.80
Purchase #2	$91.46	13.156%	$103.4925	$103.49	$103.50	$103.50
Purchase #3	$220.42	3.651%	$228.4675	$228.47	$228.45	$228.50
Purchase #4	$62.36	7.628%	$67.1168	$67.12	$67.10	$67.10
Purchase #5	$55.78	13.298%	$63.1976	$63.20	$63.20	$63.20
Purchase #6	$233.32	12.495%	$262.4733	$262.47	$262.45	$262.50
Purchase #7	$45.96	8.702%	$49.9594	$49.96	$49.95	$50.00
7 purchase totals =	$932.76		$1,013.5255	$1,013.53	$1,013.45	$1,013.60