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	$187.61	13.456%	$212.8548	$212.85	$212.85	$212.90
Purchase #2	$63.45	12.847%	$71.6014	$71.60	$71.60	$71.60
Purchase #3	$52.75	8.505%	$57.2364	$57.24	$57.25	$57.20
Purchase #4	$112.39	9.651%	$123.2368	$123.24	$123.25	$123.20
Purchase #5	$217.37	7.460%	$233.5858	$233.59	$233.60	$233.60
Purchase #6	$160.99	13.704%	$183.0521	$183.05	$183.05	$183.10
Purchase #7	$140.79	6.564%	$150.0315	$150.03	$150.05	$150.00
7 purchase totals =	$935.35		$1,031.5988	$1,031.60	$1,031.65	$1,031.60