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	$145.80	9.764%	$160.0359	$160.04	$160.05	$160.00
Purchase #2	$90.31	6.820%	$96.4691	$96.47	$96.45	$96.50
Purchase #3	$74.37	6.488%	$79.1951	$79.20	$79.20	$79.20
Purchase #4	$49.35	4.616%	$51.628	$51.63	$51.65	$51.60
Purchase #5	$139.39	13.732%	$158.531	$158.53	$158.55	$158.50
Purchase #6	$6.32	4.242%	$6.5881	$6.59	$6.60	$6.60
Purchase #7	$178.53	10.125%	$196.6062	$196.61	$196.60	$196.60
7 purchase totals =	$684.07		$749.0534	$749.07	$749.10	$749.00