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	$91.55	3.566%	$94.8147	$94.81	$94.80	$94.80
Purchase #2	$166.47	5.661%	$175.8939	$175.89	$175.90	$175.90
Purchase #3	$150.48	12.520%	$169.3201	$169.32	$169.30	$169.30
Purchase #4	$81.74	10.573%	$90.3824	$90.38	$90.40	$90.40
Purchase #5	$153.68	12.510%	$172.9054	$172.91	$172.90	$172.90
Purchase #6	$169.28	5.370%	$178.3703	$178.37	$178.35	$178.40
Purchase #7	$158.38	9.816%	$173.9266	$173.93	$173.95	$173.90
7 purchase totals =	$971.58		$1,055.6134	$1,055.61	$1,055.60	$1,055.60