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	$186.57	5.523%	$196.8743	$196.87	$196.85	$196.90
Purchase #2	$43.76	10.656%	$48.4231	$48.42	$48.40	$48.40
Purchase #3	$237.72	11.563%	$265.2076	$265.21	$265.20	$265.20
Purchase #4	$211.91	11.108%	$235.449	$235.45	$235.45	$235.40
Purchase #5	$83.75	12.435%	$94.1643	$94.16	$94.15	$94.20
Purchase #6	$180.86	13.536%	$205.3412	$205.34	$205.35	$205.30
Purchase #7	$19.60	11.450%	$21.8442	$21.84	$21.85	$21.80
7 purchase totals =	$964.17		$1,067.3037	$1,067.29	$1,067.25	$1,067.20