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	$226.58	3.144%	$233.7037	$233.70	$233.70	$233.70
Purchase #2	$103.81	10.689%	$114.9063	$114.91	$114.90	$114.90
Purchase #3	$203.95	13.159%	$230.7878	$230.79	$230.80	$230.80
Purchase #4	$157.37	9.571%	$172.4319	$172.43	$172.45	$172.40
Purchase #5	$33.80	10.587%	$37.3784	$37.38	$37.40	$37.40
Purchase #6	$39.39	8.229%	$42.6314	$42.63	$42.65	$42.60
Purchase #7	$156.27	10.235%	$172.2642	$172.26	$172.25	$172.30
7 purchase totals =	$921.17		$1,004.1037	$1,004.10	$1,004.15	$1,004.10