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	$162.63	9.871%	$178.6832	$178.68	$178.70	$178.70
Purchase #2	$137.72	6.229%	$146.2986	$146.30	$146.30	$146.30
Purchase #3	$55.55	3.726%	$57.6198	$57.62	$57.60	$57.60
Purchase #4	$173.94	7.809%	$187.523	$187.52	$187.50	$187.50
Purchase #5	$90.28	7.796%	$97.3182	$97.32	$97.30	$97.30
Purchase #6	$78.70	4.812%	$82.487	$82.49	$82.50	$82.50
Purchase #7	$180.90	13.413%	$205.1641	$205.16	$205.15	$205.20
7 purchase totals =	$879.72		$955.0939	$955.09	$955.05	$955.10