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	$111.91	3.108%	$115.3882	$115.39	$115.40	$115.40
Purchase #2	$130.86	4.247%	$136.4176	$136.42	$136.40	$136.40
Purchase #3	$6.25	7.784%	$6.7365	$6.74	$6.75	$6.70
Purchase #4	$136.33	11.787%	$152.3992	$152.40	$152.40	$152.40
Purchase #5	$100.56	5.119%	$105.7077	$105.71	$105.70	$105.70
Purchase #6	$151.50	4.484%	$158.2933	$158.29	$158.30	$158.30
Purchase #7	$14.50	5.781%	$15.3382	$15.34	$15.35	$15.30
7 purchase totals =	$651.91		$690.2807	$690.29	$690.30	$690.20