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	$50.92	10.841%	$56.4402	$56.44	$56.45	$56.40
Purchase #2	$103.28	11.394%	$115.0477	$115.05	$115.05	$115.00
Purchase #3	$53.67	3.624%	$55.615	$55.62	$55.60	$55.60
Purchase #4	$137.35	10.232%	$151.4037	$151.40	$151.40	$151.40
Purchase #5	$205.44	11.772%	$229.6244	$229.62	$229.60	$229.60
Purchase #6	$85.28	5.350%	$89.8425	$89.84	$89.85	$89.80
Purchase #7	$244.59	4.152%	$254.7454	$254.75	$254.75	$254.70
7 purchase totals =	$880.53		$952.7189	$952.72	$952.70	$952.50