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	$145.53	5.565%	$153.6287	$153.63	$153.65	$153.60
Purchase #2	$30.86	5.703%	$32.6199	$32.62	$32.60	$32.60
Purchase #3	$68.65	7.627%	$73.8859	$73.89	$73.90	$73.90
Purchase #4	$181.70	3.670%	$188.3684	$188.37	$188.35	$188.40
Purchase #5	$35.46	13.160%	$40.1265	$40.13	$40.15	$40.10
Purchase #6	$183.89	3.219%	$189.8094	$189.81	$189.80	$189.80
Purchase #7	$73.47	6.729%	$78.4138	$78.41	$78.40	$78.40
7 purchase totals =	$719.56		$756.8526	$756.86	$756.85	$756.80