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	$230.94	13.769%	$262.7381	$262.74	$262.75	$262.70
Purchase #2	$6.64	13.209%	$7.5171	$7.52	$7.50	$7.50
Purchase #3	$111.47	11.788%	$124.6101	$124.61	$124.60	$124.60
Purchase #4	$148.40	11.850%	$165.9854	$165.99	$166.00	$166.00
Purchase #5	$85.32	7.609%	$91.812	$91.81	$91.80	$91.80
Purchase #6	$205.86	13.246%	$233.1282	$233.13	$233.15	$233.10
Purchase #7	$125.70	13.274%	$142.3854	$142.39	$142.40	$142.40
7 purchase totals =	$914.33		$1,028.1763	$1,028.19	$1,028.20	$1,028.10