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	$94.57	13.179%	$107.0334	$107.03	$107.05	$107.00
Purchase #2	$111.82	10.497%	$123.5577	$123.56	$123.55	$123.60
Purchase #3	$115.58	10.414%	$127.6165	$127.62	$127.60	$127.60
Purchase #4	$49.34	3.584%	$51.1083	$51.11	$51.10	$51.10
Purchase #5	$40.70	9.709%	$44.6516	$44.65	$44.65	$44.70
Purchase #6	$33.72	13.821%	$38.3804	$38.38	$38.40	$38.40
Purchase #7	$137.31	4.465%	$143.4409	$143.44	$143.45	$143.40
7 purchase totals =	$583.04		$635.7888	$635.79	$635.80	$635.80