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	$217.49	3.612%	$225.3457	$225.35	$225.35	$225.30
Purchase #2	$199.91	5.157%	$210.2194	$210.22	$210.20	$210.20
Purchase #3	$131.78	5.366%	$138.8513	$138.85	$138.85	$138.90
Purchase #4	$118.33	4.636%	$123.8158	$123.82	$123.80	$123.80
Purchase #5	$241.78	13.782%	$275.1021	$275.10	$275.10	$275.10
Purchase #6	$42.56	8.108%	$46.0108	$46.01	$46.00	$46.00
Purchase #7	$49.97	13.675%	$56.8034	$56.80	$56.80	$56.80
7 purchase totals =	$1,001.82		$1,076.1485	$1,076.15	$1,076.10	$1,076.10