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	$219.69	3.375%	$227.1045	$227.10	$227.10	$227.10
Purchase #2	$137.49	4.773%	$144.0524	$144.05	$144.05	$144.10
Purchase #3	$114.60	8.151%	$123.941	$123.94	$123.95	$123.90
Purchase #4	$189.31	5.868%	$200.4187	$200.42	$200.40	$200.40
Purchase #5	$42.26	12.465%	$47.5277	$47.53	$47.55	$47.50
Purchase #6	$47.88	10.785%	$53.0439	$53.04	$53.05	$53.00
Purchase #7	$68.38	3.202%	$70.5695	$70.57	$70.55	$70.60
7 purchase totals =	$819.61		$866.6577	$866.65	$866.65	$866.60