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	$156.66	3.265%	$161.7749	$161.77	$161.75	$161.80
Purchase #2	$109.93	13.523%	$124.7958	$124.80	$124.80	$124.80
Purchase #3	$62.51	4.410%	$65.2667	$65.27	$65.25	$65.30
Purchase #4	$145.64	7.442%	$156.4785	$156.48	$156.50	$156.50
Purchase #5	$90.79	13.609%	$103.1456	$103.15	$103.15	$103.10
Purchase #6	$47.54	13.208%	$53.8191	$53.82	$53.80	$53.80
Purchase #7	$152.99	12.696%	$172.4136	$172.41	$172.40	$172.40
7 purchase totals =	$766.06		$837.6942	$837.70	$837.65	$837.70