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	$151.42	3.587%	$156.8514	$156.85	$156.85	$156.90
Purchase #2	$121.90	10.197%	$134.3301	$134.33	$134.35	$134.30
Purchase #3	$57.95	12.772%	$65.3514	$65.35	$65.35	$65.40
Purchase #4	$142.62	7.630%	$153.5019	$153.50	$153.50	$153.50
Purchase #5	$200.51	10.787%	$222.139	$222.14	$222.15	$222.10
Purchase #6	$153.55	10.728%	$170.0228	$170.02	$170.00	$170.00
Purchase #7	$52.87	13.649%	$60.0862	$60.09	$60.10	$60.10
7 purchase totals =	$880.82		$962.2828	$962.28	$962.30	$962.30