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	$43.54	9.487%	$47.6706	$47.67	$47.65	$47.70
Purchase #2	$198.34	5.384%	$209.0186	$209.02	$209.00	$209.00
Purchase #3	$64.83	7.620%	$69.77	$69.77	$69.75	$69.80
Purchase #4	$33.70	10.374%	$37.196	$37.20	$37.20	$37.20
Purchase #5	$59.77	4.194%	$62.2768	$62.28	$62.30	$62.30
Purchase #6	$131.94	8.182%	$142.7353	$142.74	$142.75	$142.70
Purchase #7	$65.28	8.139%	$70.5931	$70.59	$70.60	$70.60
7 purchase totals =	$597.40		$639.2604	$639.27	$639.25	$639.30