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	$202.60	10.316%	$223.5002	$223.50	$223.50	$223.50
Purchase #2	$134.98	11.587%	$150.6201	$150.62	$150.60	$150.60
Purchase #3	$102.44	9.732%	$112.4095	$112.41	$112.40	$112.40
Purchase #4	$85.32	9.104%	$93.0875	$93.09	$93.10	$93.10
Purchase #5	$157.68	11.792%	$176.2736	$176.27	$176.25	$176.30
Purchase #6	$172.76	13.819%	$196.6337	$196.63	$196.65	$196.60
Purchase #7	$125.28	7.447%	$134.6096	$134.61	$134.60	$134.60
7 purchase totals =	$981.06		$1,087.1342	$1,087.13	$1,087.10	$1,087.10