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	$49.76	8.184%	$53.8324	$53.83	$53.85	$53.80
Purchase #2	$45.36	6.724%	$48.41	$48.41	$48.40	$48.40
Purchase #3	$191.65	12.319%	$215.2594	$215.26	$215.25	$215.30
Purchase #4	$123.40	11.276%	$137.3146	$137.31	$137.30	$137.30
Purchase #5	$54.85	13.410%	$62.2054	$62.21	$62.20	$62.20
Purchase #6	$87.81	13.484%	$99.6503	$99.65	$99.65	$99.70
Purchase #7	$72.60	7.286%	$77.8896	$77.89	$77.90	$77.90
7 purchase totals =	$625.43		$694.5617	$694.56	$694.55	$694.60