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	$53.94	11.620%	$60.2078	$60.21	$60.20	$60.20
Purchase #2	$162.52	11.831%	$181.7477	$181.75	$181.75	$181.70
Purchase #3	$111.71	3.632%	$115.7673	$115.77	$115.75	$115.80
Purchase #4	$90.78	10.764%	$100.5516	$100.55	$100.55	$100.60
Purchase #5	$51.60	6.407%	$54.906	$54.91	$54.90	$54.90
Purchase #6	$152.87	9.754%	$167.7809	$167.78	$167.80	$167.80
Purchase #7	$191.59	7.198%	$205.3806	$205.38	$205.40	$205.40
7 purchase totals =	$815.01		$886.3419	$886.35	$886.35	$886.40