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	$55.44	12.144%	$62.1726	$62.17	$62.15	$62.20
Purchase #2	$55.92	8.574%	$60.7146	$60.71	$60.70	$60.70
Purchase #3	$5.28	4.694%	$5.5278	$5.53	$5.55	$5.50
Purchase #4	$227.54	7.456%	$244.5054	$244.51	$244.50	$244.50
Purchase #5	$93.38	10.859%	$103.5201	$103.52	$103.50	$103.50
Purchase #6	$20.94	4.260%	$21.832	$21.83	$21.85	$21.80
Purchase #7	$51.51	13.157%	$58.2872	$58.29	$58.30	$58.30
7 purchase totals =	$510.01		$556.5597	$556.56	$556.55	$556.50